Eye-Safe Dermatologic Treatment Apparatus and Method

ABSTRACT

A dermatologic treatment apparatus is disclosed which includes one or more housings with at least one housing configured for manipulation in a dermatologic treatment procedure, a light source, and an electrical circuit. The circuit energizes the light source to produce output light pulses. A light path includes an aperture through which eye-safe light pulses are propagated having properties sufficient for providing efficacious treatment. An optical diffuser is disposed along the light path to reduce the integrated radiance to an eye-safe level. The apparatus produces an output fluence not less than 4 J/cm 2 .

RELATED APPLICATIONS/PRIORITY

This application claims the benefit of priority under Section 35 USC119(e) to U.S. provisional patent applications No. 60/450,243, filedFeb. 25, 2003; 60/450,598, filed Feb. 26, 2003; 60/451,091, filed Feb.28, 2003; 60/452,304, filed Mar. 4, 2003; 60/451,981, filed Mar. 4,2003; 60/452,591, filed Mar. 6, 2003; 60/456,379, filed Mar. 20, 2003;60/456,586, filed Mar. 21, 2003; 60/458,861, filed Mar. 27, 2003; and60/472,056, filed May 20, 2003 and also U.S. patent application Ser. No.10/783,603, filed Feb. 19, 2004, all of which are incorporated herein byreference.

BACKGROUND

1. Field of the Invention

The invention relates to a dermatologic treatment apparatus and method,and particularly to an apparatus that is light-based, yet eye-safe.

2. Description of the Related Art

The introduction of specialized lasers for physician-performed epilationin 1996 (and intense-pulsed light, or IPL, sources shortly thereafter)represented the first real advance in the treatment of unwanted hairsince the invention of electrolysis in the late 1800's. The use oflasers and flashlamps in these devices has not only proven to be safeand effective, but unlike electrolysis allows for the treatment ofmultiple hairs at a time, greatly improving coverage rate.

Light-based epilation with lasers is often termed “laser hair removal”,although this term is strictly correct only when follicles undergosufficient thermal damage to permanently prevent the growth of new hairs(“permanent hair reduction”). Procedures that thermally damage folliclesto induce a delay in hair regrowth are more accurately described ashair-regrowth inhibition.

Methods and devices for light-based epilation are now widespread and anestimated three million people worldwide have undergone treatment. Thisrepresents a very small section of the potential market, largely becauseof the high cost and inconvenience associated with physician-basedprocedures and devices. As a result, there is a desire for lower cost,more compact devices that would lower the cost of physician-basedtreatments and, ultimately, help enable salon and consumer markets.There is also a desire for devices with enhanced eye safety.

The introduction of the LightSheer Diode Laser System by Star Medical in1997 for hair-regrowth inhibition (and subsequently, for permanent hairreduction) marked the beginning of one of the most successful aestheticlaser applications for the dermatologist's office. With several thousandsystems installed worldwide, the safety and efficacy of these andsimilar devices that followed have been well established. Other suchdevices include the SLP 1000 (LC 100) diode laser of Palomar MedicalTechnologies, the Apex 800 diode laser of IRIDEX Corporation, and the F1diode laser of Opus Medical, Inc.

The radiant exposure applied to the skin (often referred to as“fluence”, expressed in joules per square centimeter) by this class ofdevices is typically in the 10-40 J/cm² range at a wavelength ofnominally 800 nanometers. It was initially believed that pulse durationsin the 5-30 ms range are optimum; however, subsequent studies showedthat longer pulses (up to at least several hundred milliseconds) canquite effectively achieve hair-regrowth inhibition, and can also reduceepidermal heating for a given fluence when a heat conduction path isprovided (e.g., by incorporating an output window made of sapphire incontact with the skin).

The high efficiency and small size of the semiconductor diode lasersutilized in these devices generally permit the manufacture of compactsystems (typically 1-3 cubic feet in volume) and simple 115 VACoperation. However, the systems typically weigh at least 25-100 poundsand sell in the range of $40,000 to $90,000. A much lower cost, trulyportable device would make this popular procedure much more widelyavailable.

Lasers and intense light sources have gained increasing acceptance amongdermatologists for effective treatment of a wide range of applications,such as hair-regrowth inhibition and permanent hair reduction, removalof tattoos, treatment of birthmarks, and facial resurfacing. It is wellunderstood by medical professionals, however, that such light sourcesare capable of serious eye damage or blindness. To achieve reasonableefficacy with many light-based dermatologic procedures, such asreduction of unwanted hair or destruction of small blood vessels, thefluence on the skin typically exceeds 1 J/cm². These devices produce afluence at the human eye that is much greater than the maximumpermissible exposure, causing such devices and the treatments performedwith them to be extremely hazardous if not used or conducted properly.These procedures therefore involve the undertaking of adequate safetymeasures to protect the eyes of not only the patient, but the laseroperator and any other personnel that may be in the same area. (See, forexample, IEC Technical Report 60825-8, Safety of laserproducts—Guideline for the safe use of medical laser equipment.) Asstated in the IEC report, with some medical lasers the retina may beexposed to an irradiance that is more than 100,000 times higher than theirradiance incident on the skin or cornea, due to the focusing action ofthe eye.

With proper safety precautions, such as safety goggles and training ofpersonnel, the risk of eye damage can be greatly reduced. As aconsequence, reports of eye injuries to either patients or staff arerare in medical settings. However, risk of eye injury is a constantconcern.

The safety of a light-based dermatologic device can be increased byincorporation of a contact sensor that enables device operation onlywhen in the sensor is in contact with a surface, such as a person'sskin. For example, the light source (laser, light-emitting diode,flashlamp, etc.) can be placed within a housing having a single open endthrough which the light propagates; a contact sensor at this open endcan enable operation of the device only if the housing is placed upagainst a contacted surface. In this manner light can only propagateinto or through the surface against which the device is placed. However,use of any type of sensor added to increase eye safety adds complexityand may, of course, fail. Thus, the ideal dermatologic treatment deviceand method would not depend on electronic circuitry or user compliancewith safety eyewear for safe use.

Thus it is highly desirable that any light-based device intended formedical application be designed to minimize possible eye damage for agiven level of output fluence or therapeutic benefit, by increasing theinherent eye safety of the light. Existing laser hair reduction devices,for example, are much more hazardous to the eye than necessary becausetheir output is highly directional and easily focused by the eye. Iftheir output could be made more highly divergent and/or to have reducedspatial coherence, there would be a greatly reduced risk of eye injury,without significant loss of efficacy.

Examples of office-based, light-based systems for dermatologicaltreatment are described in U.S. Pat. Nos. 6,508,813, 6,277,111,6,197,020, 6,096,029, 5,885,273, 5,824,023, and 4,232,678, and U.S.published application no. 2002/0005475, and published PCT applicationno. WO 03/049633. The '5475 published application uses a contact sensorfor enabling laser pulses only when the handpiece is in good contactwith a patient's skin. One problem with application of such a device ina home use, self-care setting is that a small child, or personattempting to treat eye lashes or eye brows with the device, may stillinadvertently shine pulses into their eyes and potentially causepermanent damage to their vision. Similar eye-safety problems would beapparent in a home use, self-care application of the devices describedin each of the above-mentioned patents.

The '49633 published application addresses the eye-safety issue byproviding a diffusing unit. However, that device is far too bulky,complex and expensive for home use. The device includes a substantiallynon-portable laser floor unit and an extensible handpiece connected by along beam delivery light guide. In addition, other safety issues existfor this device. For example, a home use, self-care setting may not beequipped to handle the electrical safety issues of a device that drawshigh current from a wall outlet. Most importantly, however, theinvention described in the application addresses enhanced eye safetyfrom a collimated laser beam, convergent laser beam, concentratedmultiple laser beams or a fiber guided beam, and from monochromaticsources. In contrast, divergent light sources can be rendered eye safesubstantially more easily, as described below in accordance with thepresent invention.

The '029 and '020 patents describe devices that provide fluences over100 J/cm². These fluences are generally too large to be eye-safe andepidermis-safe in use in a self-care setting. Such output fluences arelikely to give rise to fluences at the cornea potentially above theMaximum Permissible Exposure (MPE), described in more detail below,and/or may likely cause burning of the epidermal region of the treatedskin. Moreover, such fluence levels are not efficiently produced in aself-contained apparatus, such as a hand-held and battery-powered deviceas is desired for self-care and home use in accordance with anembodiment of the present invention.

Furthermore, the device described in the '029 and '020 patents providesa very small spot size between 2 and 5 millimeters in diametercorresponding to approximately 0.03 to 0.2 square centimeters in area.Such a small spot implies that only one hair is treated at a time, andin fact some sort of visual targeting is almost certainly required toensure that the spot is indeed over even a single target follicle. Also,a small spot size such as between 0.03 and 0.2 square centimetersimplies a very low coverage rate. That is, for a given number of squarecentimeters of skin containing unwanted hairs to be treated, the smallerthe spot size the longer the necessary treatment time. In addition,while a small spot size would appear to be quite advantageous in that alow energy can still generate a high fluence on the skin surface (sincefluence is energy divided by area), the fluence at some depth within theskin, e.g., where the target cells are located, is substantially reducedby scattering within the skin. That is, the smaller the spot size,especially below about 0.5 cm², the more pronounced the effectivelessening of fluence at depth relative to fluence at the surface. Inshort, if one goes to too small a spot such as is described in the '029and '020 patents, the end result can be either burning of the epidermis(to get enough fluence in the dermis) or very poor efficacy due toinadequate fluence at depth; either of these options is obviouslyundesirable.

Current State of the Art

The current state of the art of light-based epilation is well describedby considering the two general types of devices on the market. Onemarket segment encompasses devices designed and sold to physicians.Representative products include the LightSheer diode laser system nowmanufactured by Lumenis Ltd., the SLP-1000 fiber-coupled diode laser byPalomar Medical Technologies Inc., the Quantum flash lamp systemmanufactured by Lumenis Ltd., and the CoolGlide Excel YAG laser by AltusInc. The physician devices are characterized by (a) established efficacyas confirmed by FDA clearance, (b) practical coverage rate, (c) highcost, and (d) relatively large size having a physical design where ahandpiece is attached to a console, and (e) output fluences representinga severe eye hazard. These devices provide efficacious and practicallight-based epilation and generally involve a peak optical power greaterthan 50 W, output fluence of greater than 10 J/cm², spot size greaterthan 0.5 cm², and a coverage rate greater than 10 cm²/min. Examples ofthese office-based devices are described in the patent literature citedabove, and further examples may be found in other references citedherein.

The other market segment comprises the limited number of consumerlight-based epilation devices. It is believed that there are no personallight-based epilators currently on the market in the United States. Atpresent, the most developed market for consumer light-based devices isAsia, and, in particular, Japan, where there are tens of products on themarket. The devices by Ya-Man Ltd. of Tokyo are typical of the state ofthe art for these products in Japan. These consumer devices arecharacterized by (a) greatly reduced or no efficacy due to low peakpower (.about. 1 W or less) and small spot size (.about. 0.1 cm² orless), (b) slow coverage rate due to the small spot size and involvingthe targeting of individual hair follicles, (c) low cost, (d) relativelysmall size having a physical design where a handpiece is attached to aconsole or corded to a wall power supply, and (e) output fluencesexceeding eye safety limits.

The inventors of an embodiment of the present invention have recognizedthat a method and device that could provide effective and practicalepilation in an entirely handheld and cordless device would bedesirable. By cordless and handheld, it is preferably meant that thedevice is self-contained in operation, and has, for example, a volumeless than 1500 cm³ and a weight less than 1 kg. Such a handheld andcordless device would be substantially less cumbersome than console andhandpiece devices and allow the operator to much more convenientlyposition the device into orientations that are required to best treat adesired region of skin. In addition, it allows easy portability, andfreedom to perform treatments in the absence of electricity from a walloutlet. In order to be an effective and practical treatment device, peakoptical output powers greater than 10 W, output fluences greater than 4J/cm², spot sizes greater than 0.25 cm², and coverage rates greater than10 cm²/min may be generally involved.

While other light sources for hair-regrowth inhibition, such as intensepulsed light, and a variety of lasers, are now commercially available tophysicians, diode laser systems have proven to be among the mostsuccessful. These devices typically incorporate laser diode barsoperating at a wavelength of approximately 800 nm. The systems range inpeak optical power from about 90 watts to nearly 3,000 watts.

Discrete laser diodes are limited in peak power to roughly one watt.While this low power may be adequate for treating individual hairs (suchas the Ya-Man device manufactured in Japan), treatment of multiple hairsat a time for rapid treatment of extended areas requires peak opticalpowers of roughly 25 watts or more. Thus diode laser bars, rather thandiscrete diode laser devices, are incorporated into the diode-basedoffice products named above. The success of these hair-regrowthinhibition systems incorporating laser diode bars, used by doctors andnurses in an office setting, has fueled interest in the development ofhome-use devices. The inconvenience of multiple visits to the doctor'soffice has also increased interest in devices that can be used safelyand privately at home. Ideally, such a consumer device would be compact,inexpensive and battery powered, while incorporating proven laser diodebar technology. Unfortunately, because of the very high currentrequirement (.about. 40 A) of laser diode bars, it is generally acceptedthat any such device could not be powered by batteries, but rather by anelectrical cord to a wall outlet.

Examples of other dermatologic devices are described at U.S. Pat. No.6,533,775, and at U.S. published patent applications no. 2003/0004499and 2002/0097587, and in other references incorporated by referenceabove and below herein.

Although potentially eye-safe, the U.S. Pat. No. 6,533,775 describes amechanical hair removal device, and not a light-basedhair-regrowth-inhibition apparatus. The device described in the '775patent includes a light source that reacts chemically with skin creamapplied to the surface in order to reduce the onset time. The lightproduced by the mechanical hair removal device is not for effectingthermal damage of hair follicles to inhibit regrowth. The light is notdesigned to penetrate through the cream to create any thermal injury totargets within the dermis.

The '97587 application describes a device with variable current control.This device is not designed for medical applications. The reference alsodoes not provide any output fluences, wavelengths or pulse lengths thatmight by chance render the fluence at the eye of a person to be underthe MPE. There would simply have to be many modifications made to thisdevice to render it eye-safe for home use and to render it efficaciousfor dermatologic treatment for hair-regrowth inhibition.

The '4499 application describes a device that is described as beingdesigned to inhibit hair regrowth. The '4499 application refers to itsprocedure as bio-stimulation to produce bio-inhibition, and in any case,it is non-thermal. This is a wholly separate field fromhair-regrowth-inhibiting devices that operate by causing thermal damageto hair follicles. The '4499 reference uses much lower fluences (orintensities) than would be efficacious for causing thermal damage to ahair follicle to produce hair-regrowth inhibition.

The design of a handheld device for hair-regrowth inhibition requiresclever circuit design, and implementation of a dermatologic treatmentdevice that is efficacious and yet eye-safe requires novel opticaldesign. Therefore it has appeared up to now that the creation of alow-cost, light-based dermatologic treatment device, such as a home-usehair-regrowth-inhibiting device that is effective, compact,battery-powered, and incorporates a diode laser or other light source,is an unachievable goal. However, recent advances in both lighttechnology and microelectronics have made possible the present inventionof dermatologic devices that are both efficacious and affordable to theaverage consumer. In some embodiments, these devices can be sufficientlycompact as to be entirely handheld and battery-powered. In otherembodiments, these devices can be made to be effective for a variety ofdermatologic procedures, and yet eye-safe. They are the objects of thepresent invention, and are described in more detail below.

SUMMARY OF THE INVENTION

Therefore in view of and in accordance with the above, a dermatologictreatment apparatus includes a one or more housings with at least onehousing configured for manipulation in a dermatologic treatmentprocedure, a light source within at least one of the housings, and anelectrical circuit. The circuit energizes the light source to produceoutput light pulses. A housing contains a light path from the lightsource to an aperture through which eye-safe light pulses are propagatedout of at least one of the housings having properties sufficient forproviding efficacious treatment. An optical diffuser is disposed alongthe light path to reduce the integrated radiance to an eye-safe level.The apparatus produces an output fluence not less than 4 J/cm². In use,the dermatologic apparatus produces a fluence on the skin surface thatis sufficient for efficacious treatment and has an integrated radianceinsufficient to cause eye damage.

In one aspect, the light source is a divergent light source. Forexample, the light source has a divergence that is greater than 1degree, and is preferably greater than 6 degrees. In other aspects, theoptical diffuser may be transmissive or reflective.

A transmissive diffuser may include a bulk scattering diffuser mediumsuch as opal glass, PTFE, thin Spectralon, or combinations thereof. Thetransmissive diffuser may also include a diffusive surface that isrefractive or diffractive, or both, and may include a random surfacesuch as ground glass, sandblasted glass or plastic, etched glass orplastic, or molded materials produced by a randomly textured mold, orcombinations thereof. The transmissive diffuser may also include apatterned surface such as a holographic or Fresnel pattern. Thereflective diffuser may include a rough surface such as sandblastedmetal, plastic or ceramic, or etched metal, plastic, or ceramic, ormolded materials produced by a rough mold, or combinations thereof, ormay include a bulk diffuser or bulk diffuser coating, or both, such ascomprising opal glass, Spectralon, PTFE, diffuse white coatings,Duraflect, or combinations thereof.

A mixer may be disposed along the light path for distributing light moreuniformly at the aperture. The principal optical axis of the lightemitted by the source striking the diffuser is, in one embodiment, notparallel to the normal of the surface of the diffuser.

In another aspect, the light source is a diode laser light source, aflashlamp source, or a light emitting diode (LED) source. In accordancewith any of these aspects, the apparatus produces an output fluencebetween 4 J/cm² and 100 J/cm² wherein the fluence at the eye of a personis less than a maximum permissible exposure (MPE), such MPE having avalue in J/cm² equal to 1.8 10⁻³ t^(0.75) C₄C₆, where C₄=1 for 400 nm to700 nm light and C₄=10^(0.002(λ-700)) for infrared wavelengths λ in nmfrom 700 nm to 1050 nm and C₄=5 for 1050 nm to 1100 nm light, and C₆ isa number between 1 and 66.7 for a diffuse source, and t is the pulseduration in seconds. The majority of the energy of a light pulse iscontained within the spectral band of 700 nm to 1100 nm. The lightpulses are emitted at a pulse repetition frequency between 0.1 Hz and 2Hz, have pulse durations between 10 milliseconds and 1 second, have apeak power between 10 watts and 120 watts, and produce a spot sizebetween 0.25 cm² and 5 cm².

The dermatologic treatment procedure may involve photorejuvenation. Inthis case, the light source is preferably a flashlamp light source. Atleast a majority of the energy of the output light pulses emitted by thelight source is between 500 nm and 1100 nm.

The dermatologic treatment apparatus may be configured for performing atleast temporary hair-regrowth inhibition, for treating acne, fortreating benign pigmented lesions, for vascular treatment, and/or forskin texture or wrinkle treatment, or both.

A dermatologic treatment method is also provided for treating a person'sskin. The method may be used in any of the procedures mentioned, and mayutilize an apparatus according to any of the above aspects that are notrepeated here. A handpiece assembly of a dermatologic treatment deviceis gripped in a person's hand. The handpiece assembly is positioned suchthat an output window component of the device contacts a region of theepidermis of a same or different person. A light source is energizedwith an electrical circuit to produce output light pulses. The lightpulses generated by the light source are transmitted along a light pathincluding an aperture through which eye-safe light pulses are propagatedfrom the handpiece having properties sufficient for efficacioustreatment including producing an output fluence not less than 4 J/cm².The light pulses are optically diffused along the light path to reducethe integrated radiance to an eye-safe level. Then, the device ismanipulated in a skin treatment procedure that produces a fluence on theskin that is sufficient for efficacious treatment and yet has anintegrated radiance insufficient to cause eye damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a dermatologic treatment apparatus inaccordance with a first embodiment that is self-contained andbattery-powered.

FIG. 2A schematically illustrates a dermatologic treatment apparatus inaccordance with a second embodiment in contact with a person's skin,that is eye-safe and that incorporates a transmissive diffuser.

FIG. 2B schematically illustrates a dermatologic treatment apparatus inaccordance with a third embodiment in contact with a person's skin, thatis eye-safe and that incorporates a reflective diffuser.

FIGS. 3A and 3B schematically illustrate an optical diffuser inaccordance with the second embodiment.

FIG. 3C schematically illustrates an optical diffuser in accordance withthe third embodiment.

FIG. 3D schematically illustrates yet another type of optical diffuserthat has a spatially uniform output.

FIG. 3E schematically illustrates the optical diffuser of FIG. 3C incontact with a person's skin during a hair-regrowth-inhibiting procedureor other dermatologic procedure.

FIG. 4 schematically illustrates the divergence of a laser beamtransmitted through a bi-concave lens.

FIG. 5 schematically illustrates a hair-regrowth-inhibiting apparatus inaccordance with the second embodiment.

FIG. 6 schematically illustrates a front perspective view of aself-contained housing of a hair-regrowth-inhibiting apparatus inaccordance with a preferred embodiment.

FIG. 7 schematically illustrates a rear perspective view of theself-contained housing of the hair-regrowth-inhibiting apparatus of FIG.6.

FIG. 8 schematically illustrates indicator lights of thehair-regrowth-inhibiting apparatus of FIGS. 6-7.

FIG. 9 schematically illustrates a perspective view of an AlGaAs laserdiode bar.

FIG. 10 schematically illustrates a cross-sectional view of ahair-regrowth-inhibiting apparatus in accordance with the secondembodiment.

FIG. 11 schematically illustrates components of an electrical circuit inaccordance with a preferred embodiment.

FIG. 12 schematically illustrate components of an electrical circuit forpowering a laser diode light source with batteries through a FET-basedswitch in accordance with a preferred embodiment.

INCORPORATION BY REFERENCE

What follows is a list of citations corresponding to references whichare, in addition to those references cited above and below, andincluding that which is described as background and the inventionsummary, hereby incorporated by reference into the detailed descriptionof the preferred embodiments below, as disclosing alternativeembodiments of elements or features of the preferred embodiments thatmay not otherwise be set forth in detail below. A single one or acombination of two or more of these references may be consulted toobtain a variation of the elements or features of preferred embodimentsdescribed in the detailed description below. Further patent, patentapplication and non-patent references are cited in the writtendescription and are also incorporated by reference into the preferredembodiment with the same effect as just described with respect to thefollowing references:

U.S. Pat. Nos. 4,232,678, 4,551,628, 4,592,353, 4,690,141, 5,057,104,5,059,192, 5,075,971, 5,109,465, 5,401,270, 5,405,368, 5,431,647,5,486,172, 5,700,240, 5,728,090, 5,743,901, 5,820,625, 5,824,023,5,871,521, 5,885,273, 6,059,765, 6,096,029, 6,138,041, 6,160,831,6,188,495, 6,197,020, 6,228,074, 6,273,884, 6,277,111, 6,280,438,6,290,713, 6,440,122, 6,441,943, 6,508,813, 6,511,475, 6,514,242,6,516,013, 6,517,532, 6,533,775, 6,548,781, 6,563,853 and 6,641,044;United States published applications no. 2003/0233138, 2003/0032950,2003/0004499, 2002/0128635, 2002/0097587, 2002/0091377, 20020015430, and2002/0005475; and

U.S. provisional patent applications No. 60/451,091, filed Feb. 28,2003; 60/456,379, filed Mar. 20, 2003; 60/458,861, filed Mar. 27, 2003;60/472,056, filed May 20, 2003; 60/450,243, filed Feb. 25, 2003;60/450,598, filed Feb. 26, 2003; 60/452,304, filed Mar. 4, 2003;60/451,981, filed Mar. 4, 2003; 60/452,591, filed Mar. 6, 2003; and60/456,586, filed Mar. 21, 2003; and

Published PCT applications no. WO 03/049633;

European published application no. EP 1 168 535, EP 0 761 257, EP 1 116476 and

EP 0 933 096; French patent document no. FR2665366;

Japanese patent documents no. JP2000300683, and JP11244295;

German patent document no. DE19629978; and

Sliney, et al., Safety with Lasers and Other Optical Sources, AComprehensive Handbook, Plenum Press (1980); and

Hode, L, “Are lasers more dangerous than IPL instruments?” Lasers inSurgery and Medicine, Supplement 15, 2003, p. 6; and poster presentationat corresponding conference.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A device and method are described in a first embodiment that enablelight-based dermatologic treatment with a self-contained and handhelddevice. The device embodies an advantageous combination of abattery-powered electrical circuit design, a self-contained housingmechanical design, and a light source and optical design, that enablesefficacious and practical dermatologic treatment in a cordless andhandheld manner.

The light source may be, for example, one or more semiconductor laserdiode bars that generate pulses of infrared light. To effecthair-regrowth inhibition, light from the device passes through theepidermis and is absorbed by melanin in the hair shaft and follicle. Theresulting brief temperature rise of the follicle temporarily disablesit, delaying the regrowth of hair. The device can be pulsed at arepetition rate of up to 0.5 Hz.

Effective dermatologic treatment, e.g., hair-regrowth inhibition, canoccur with standard (10-40 J/cm²) output fluences, yet with very longpulse durations (up to 1000 ms). This avoids the need for very high peaklaser powers; for example, to produce 20 J/cm² in 350 ms with a 9 mm by9 mm output area requires a optical peak power of only 46 watts. Themodest peak power requirement, in turn, reduces the electrical pulsedpower requirement, and thereby permits battery operation. Through theuse of miniature surface-mount electronic components, thermo-electric(TE) modules and advanced nickel-metal-hydride battery technology, sucha device has been invented that may be entirely handheld, with theaforementioned parameters in a preferred embodiment.

A device in accordance with a preferred first embodiment is illustratedschematically in FIG. 1. The elements shown are light source 10, mixer12, output window 14, heat-removal element 16, electrical battery 18,and housing 20. Not shown but involved in the operation of the deviceare other mechanical, electrical, and optical elements (such as atrigger, drive and control circuitry, sensors, and indicators) such asmay be described in more detail below and/or as may be understood bythose skilled in the art. That is, FIG. 1 is intended merely to serve tointroduce the device of a preferred first embodiment to be described inmore detail below.

In operation, the user charges the electrical battery 18 (by placing thedevice in a charging station, for example, that will provide electricalcharge from a wall outlet). Once charged, the user presses an outputwindow 14 or aperture 14 against the surface of the skin to be treated.The aperture or window 14 in contact with the skin is preferably made ofsapphire, because of its relatively high thermal conductivity. Theoutput aperture or window 14 may, however, be only an opening oraperture such that the window component 14 that contacts the person'sskin may be a frame of the opening. The heat-removal element 16 drawswaste heat from light source 10 and may draw heat as well from the skinby conduction through window 14 and mixer 12. The heat-removal element16 may be a thermoelectric heat exchanger that dissipates heat to thesurrounding air by use of a finned heat sink and fan; or may be a solidmaterial that acts as a heat sink due to its high heat capacity (a“thermal battery”) as described in some further detail below. The userthen activates a pulse from the light source 10 by pressing a triggerbutton. In an alternative embodiment, the electrical circuit may bedesigned so that upon sufficiently contacting the skin of a person beingtreated, a contact sensor located near the output aperture sensessufficient contact of the output window component 14 with a person'sskin so that one or more pulses may be automatically activated. Thelight pulse enters the mixer 12 which serves to distribute the lightsubstantially uniformly onto the output window 14 and ultimately intothe skin. The output window 14 is connected to the heat-removal element16 by mixer 12 and thus additionally serves as a protective heat sinkfor the skin.

To further simplify operation, the preferred device operates at a fixed,mid-range output fluence setting of nominally 20 J/cm² and a fixed,mid-range pulse duration of nominally 300-350 ms. In an alternativeembodiment, the output fluence would be continuously or discretelyadjustable. Details of the electrical circuit design are provided below.

Additional details of a preferred embodiment of a light-basedhair-regrowth-inhibition apparatus are shown in FIGS. 6-8. The exteriorof the unit housing 410 is shown schematically in these figures. FIG. 6illustrates a perspective front view and the output window 420 is shown.Trigger buttons 430 for initiating laser pulses are also shown and areeasily depressed by a left- or right-handed self-care user. Vent louversor openings 440 are also visible. A charging base 450 is shown with apower cord 460 for recharging the apparatus.

In the rear perspective view of the apparatus shown in FIG. 7, theoutput window 420 is indicated along with the vent louvers 440, as wellas an on-off button 460 and indicator lights 470. The indicator lights470 are illustrated in more detail in FIG. 8. A battery charge indicator472, an on/off indicator 474 and a ready indicator 476 are providedexamples.

The primary elements of the apparatus will preferably have a volume lessthan approximately 2000 cm³, and more preferably less than approximately1000 cm³, and a weight less than approximately one kilogram. Even morepreferably, the apparatus may have a volume less than 700 cm³ and aweight less than 700 grams. In this way, the apparatus can be grippedand firmly controlled in a self-care procedure within a user's handwithout providing stress in the user's grip and without causingexcessive fatigue during use. As illustrated in FIGS. 6-7, the apparatushas a volume of 400 cm³ and a weight of 500 g in a cordless,self-contained device. It is noted that where the term cordless is usedherein, it is meant to refer to a unit that is battery-powered and notelectrically plugged into an external outlet or power source during use.In addition, where the term self-contained is used herein, it is meantthat the unit is not physically connected to a base unit or other suchunit and is free to be manipulated without attached wires or couplings.In that sense, a self-contained housing 410 such as that illustrated inFIGS. 6-7 has the light source and batteries contained within it, suchthat the housing is not attached to any electrical cable or light guidecable that protrudes out of the housing 410. This is not to say that awireless control, or other wireless coupling, or the charging base 450cannot be included components of a unit that includes the preferredself-contained housing 410 illustrated in FIGS. 6-7; however in use, thehousing 410 is free of externally protruding physical couplings such ascontrol wires, optical cables and power cords.

Even allowing for maximum electrical, thermal, and opticalinefficiencies, control circuitry, and mechanical packing factors, thehandheld device of the preferred embodiment is highly efficient,self-contained and user friendly. Furthermore, the output parameters ofthe device establish that it is efficacious and practical in use.

In this section, additional details are provided regarding a preferredmethod of use of the apparatus. Charging the apparatus involves itsplacement into a charging base 450 shown in FIG. 6 generally overnightprior to use. Charging of the device is easily done by plugging thepower cord into a suitable AC outlet and placing the device into thecharging stand 450. Following use, the unit should be returned to thecharger 450, so that it will be fully charged for the next use. The unitmay be left in the charger 450 for extended periods of time without harmto the unit.

During charging, the left indicator light 472 (FIGS. 7-8) flashes green.When the battery is fully charged, this light will cease flashing andremain green.

Preparing the skin for maximum comfort during use involves shaving thearea to be treated prior to treatment, and then wiping with a cool, dampcloth. Because the unit relies on absorption of light by the hair shaftunder the skin, the hair should not have been previously removed byplucking or waxing. If either of these methods were performed recentlyon the area to be treated, treatment should be postponed until hairs areonce again visible.

Performing the treatment, after the unit has been fully charged,involves turning on the unit by pressing and releasing the ON-OFF button460 shown in FIG. 7. When the unit is on, the center indicator light 474shown in FIG. 8 will illuminate.

For a brief period after the power is turned on, the right indicatorlight 476 may flash, indicating that the unit is approaching the “ready”state. The right indicator light 476, when steadily green, indicatesthat the device is ready and will emit a light pulse when either of thetwo trigger buttons 430 is depressed (provided that the output window420 is in contact with skin). Two triggers 430 are provided to permitcomfortable use of the device in either hand.

To perform the treatment, the output window 420 is placed firmly againstthe shaved skin area to be treated, and either trigger 430 pressed andreleased. A beep will be preferably heard when the laser pulse iscompleted. In a particular embodiment, a beep and/or other tone orsensory indication is preferably heard when good contact is made withinthe skin indicating that the contact sensors around the window 420 arein contact with the skin and will permit the pulse to be propagated outof the housing 410. Accordingly, the self-care user will know that theunit will not generate a pulse until good contact is established and thetone is heard. In another embodiment, a beep and/or other tone orsensory indication will be heard if after making good contact with theuser's skin, the output window 420 is moved away from good contact. Thisindication is to inform the user that a pulse will not be permitted tobe propagated from the housing 410 until good contact is re-established.After the pulse-completed beep is heard, the output window 420 is movedto an adjacent area, allowing for approximately fifty-percent overlap.That is, the tip should be moved a distance about one-half the width ofthe area contacting the skin. It is not necessary to hold the triggerdown throughout the pulse. It is, however, important to maintain fullcontact between the skin and the output window 420 for the entireduration of the laser pulse. If the output window 420 is lifted from theskin prior to completion of the laser pulse, a distinct tone is soundedto alert the user, and the area should be re-treated with an additionalpulse.

The preferred maximum repetition rate of the unit is one pulse every twoseconds, and generally between one pulse every second and one pulseevery four seconds. Thus there may be a few-seconds delay before thenext beep is heard.

All of the various sounds described above serve as audible feedback andaid in the use of the device.

Second and Third Embodiments

Alternative embodiments of a dermatologic treatment device and methodincorporate an optical diffuser, described in detail below, to greatlyenhance the eye safety of the device while minimally affecting efficacy.The addition of an optical diffuser to increase the divergence and toreduce the spatial coherence of the light emitted from the device allowsthe apparatus to be classified as a Class I Laser Device under theguidelines of the U.S. Food and Drug Administration Center for Devicesand Radiological Health. This permits the use of the apparatus withouthaving to wear laser safety glasses or goggles, and most importantly,eliminates the risk of eye injury if other safety means such as thecontact sensor described above should fail.

Accordingly, a device and method for dermatologic treatment are providedin a second and third embodiment that are inherently eye-safe. That is,the device and method are effective in treating various dermatologicconditions (i.e. produce a fluence at the skin surface of greater thanabout one joule per square centimeter) and yet at the same time, whenaimed directly into the eye from any distance, produce a fluence at thehuman eye that is below the Maximum Permissible Exposure (MPE) asdefined by the American National Standards Institute (ANSI) and theInternational Electrotechnical Commission (IEC). This value for the MPEis essentially the same as the Exposure Limit (EL) published by theInternational Commission on Non-ionizing Radiation Protection (ICNIRP).

It is recognized in the design of the apparatus that, unlike manyapplications for lasers and other light sources, dermatologic treatmentdoes not generally require a highly directed beam. As long as the lightis confined in some manner within a handpiece or applicator prior to itsentering the skin surface, there is very little value in requiring thelight to strike the skin at normal incidence (i.e., light rays orientedroughly perpendicular to the skin surface). This is because the skin isa highly scattering medium, and any light rays entering the skin atnormal incidence are scattered by epidermal skin cells very near thesurface and thus are redirected into all angles. The incorporation of adiffuser accomplishes this spreading of the light rays prior to enteringthe skin, which has little impact on efficacy but greatly enhances eyesafety. It should be noted that simply increasing the divergence of acoherent source such as a laser by inclusion of a simple divergingelement (e.g., a lens) is not nearly sufficient to achieve the requisiteeye safety, due to the focusing ability of the eye and resultingintensification of that light onto the retina.

It is noted that the devices described in the second and thirdembodiments below can readily accommodate the essential elements of thefirst embodiment. That is, the eye-safe devices described in theembodiments below could be realized in a self-contained, battery-powereddevice. Alternatively, the devices described below could be corded tooperate from a conventional wall outlet during use. It is also notedthat the method of use of the devices described in the second and thirdembodiments is essentially the same as that described in the firstembodiment.

FIG. 2A schematically illustrates a dermatologic device, such as alight-based hair-regrowth-inhibition device, incorporating atransmissive diffuser in accordance with the second embodiment of theinvention. When used herein, a transmissive diffuser is intended todescribe an element incorporated into a light path having an inputsurface which the light initially strikes; and a second, output surfacefrom which light propagates. Such input and output surfaces of thetransmissive diffuser are separated by the material of the diffuseritself.

The figure schematically illustrates the device, in contact with skin150, that incorporates the use of a diffusing material 120 through whichthe light passes before leaving the apparatus though output window (orsimply an open aperture) 100. Contained within the source chamber 130 isa light source 140 that emits pulses having many advantageous features.Light source 140 may be, for example, a laser diode assembly fortreatment of a dermatological condition, and preferably includes one ortwo laser diode bars.

The diffusing material 120 is placed over an aperture in source chamber130. Light source 140 preferably does, but need not, uniformlyilluminate diffuser 120. The diffuser 120 is designed to increase thedivergence of the light emitted from light source 140, and to reduce thespatial coherence of the light source. Diffuser 120 may be made of amaterial that scatters light traveling through it, such as an opalizedglass substrate. Details regarding appropriate optical diffuser designsand materials are contained in a subsequent section describing componentdetails. In a variation of this embodiment, the inner walls of thesource chamber 130 would be coated and/or otherwise constructed of amaterial that is non-absorbing at the therapeutic wavelengths emitted bysource 140. A source chamber that is not substantially non-absorbingwould also be acceptable; however, a more intense light source 140 wouldbe involved for the same power delivered to the skin. The requirementfor additional power is not desirable, particularly in a cordless,hand-held, self-care device because energy efficiency is at a premium.

The spatial uniformity of the light may be increased through the use ofa mixing chamber 110 which may be simply a hollow tube withsubstantially non-absorbing side walls through which the light wouldpropagate prior to leaving the apparatus through output window 100. Ifthe spatial uniformity of the light at the diffuser is adequate for thedesired treatment, the mixer can be omitted, so that the diffuser 120may even be in contact with the skin and serve as the output window.Alternatively, the diffuser 120 may be located at the position shown inFIG. 2A even if it is determined that sufficient uniformity may beachieved without the function of the mixing chamber 110. It is desired,however, that the diffuser 120 not be placed so close to the lightsource 140 that substantial non-uniformity results from the light nothaving sufficiently diverged from the light source before impinging uponthe diffuser 120.

FIG. 2B schematically illustrates a dermatologic device, such as alight-based hair-regrowth-inhibition device, incorporating a reflectivediffuser in accordance with the third embodiment of the invention. Byreference to FIG. 2B, the term reflective diffuser is intended todescribe an element incorporated into a light path having a first orinput surface which the light initially strikes; however, in contrast toa transmissive diffuser, this first surface also serves as the outputsurface from which light propagates from the diffuser. It is furthernoted that the term “reflective” is used in this context to includeremitted light. That is, the diffuser may scatter or refract light aswell.

In FIG. 2B, a light-based hair-regrowth-inhibition device is illustratedin contact with skin 155 that incorporates the use of a diffusingmaterial 125 which diffuses light from source or sources 145 before thelight leaves the apparatus though output window (or simply an openaperture) 105. Contained within the chamber 115 is a light source orsources 145 that emit pulses having many advantageous features. Lightsource or sources 145 may be, for example, laser diode bars fortreatment of a dermatological condition such as unwanted hair.

The diffusing material 125 is placed within chamber 115 in a positiongenerally opposite the skin, as shown. Light source or sources 145preferably does, but need not, uniformly illuminate diffuser 125. Thediffuser 125 is designed to increase the divergence of the light emittedfrom light source or sources 145 and to reduce the spatial coherence ofthe light source or sources. Diffuser 125 may be constructed of a highlyscattering material such as PTFE, e.g., Teflon. Details regardingappropriate optical diffuser designs and materials are contained in asubsequent section describing component details. In a variation of thisembodiment, the inner walls of the chamber 115 would be coated and/orotherwise constructed of a material that is non-absorbing at thetherapeutic wavelengths emitted by source or sources 145. The spatialuniformity of the light may be increased through the use of chamber 115as a mixer which may be simply a hollow tube with substantiallynon-absorbing side walls through which the light would propagate priorto leaving the apparatus through output window 100. It is further notedthat FIG. 2B illustrates the concept of a reflective diffuser in anembodiment wherein light from the source or sources 145 is initiallydirected away from the skin 155, prior to striking diffuser 125. Thedevice in FIG. 2B could be alternatively constructed wherein light fromsource or sources 145 initially propagates in a direction toward theskin; but, prior to striking the skin, such light is redirected by amirror or mirrors back toward the diffuser 125.

Component Design

Light Source

With reference to FIG. 1, the light source 10 is preferably two diodelaser bars at a nominal wavelength of approximately 800 nm. Operatingspecifications may be, for example, 20 J/cm² output fluence, 350 mspulse duration, 0.8 cm² spot size (output aperture), and 0.5 Hz pulserepetition rate. These parameters correspond to an optical peak power of46 W and a duty cycle of about 18%; the resulting average optical poweris thus about 8 W. Diode bars operating at these parameters are about35-40% efficient; thus the average electrical power into the lightsource is about 23 W (8 W of emitted average optical power and about 15W of waste heat). The volume and weight of the light source is about 1cm³ and 10 g. Alternative embodiments for the light source include useof one diode laser bar rather than two, use of more than two diode laserbars, use of light emitting diodes (LED's), and use of a flash lamp(also known as a flash tube) or arc lamp.

Skin Contact Sensor

To prevent an inadvertent output light pulse from the device when it isnot in contact with skin, a skin contact sensor is preferablyincorporated into the tip of the preferred dermatologic treatmentapparatus. The sensor may include a ring of very small “membraneswitches” located around the circumference of the preferred sapphirewindow. The signals from the membrane switches prevent firing of thedevice unless it is in substantial contact with a contacted surface suchas skin. In an alternative embodiment, the trigger may be eliminated,and the closing of one or more membrane switches may activate one ormore light pulses. As described above, audible or other sensoryindications are preferably provided when good contact is made, and whenthe output window is displaced from a good contact position on theuser's skin such that firing is disabled until good contact is againestablished. An audible or other sensory indication is also preferablyprovided at the end of a pulse indication to provide feedback to theuser that the apparatus may be moved to another location before the nextpulse.

Charging Base

Between uses of the dermatologic treatment apparatus of the preferredembodiment, it is preferably placed in a charging base (see FIG. 6). Thecharging base may be similar to those currently produced for use withelectric toothbrushes, shavers, phones, etc. The base is connected to astandard AC outlet, and is capable of recharging the batteriesovernight.

As mentioned above, the apparatus in the second or third embodiment mayalso be corded to operate from a standard wall outlet during use,eliminating the need for a charging base.

Mixer

In the embodiment shown in FIG. 1, the mixer 12 serves to (a) to mix thelight emitted from the diode lasers to produce a uniform beam profile atthe output window 14, (b) to provide a low thermal resistance pathbetween the output window 14 and the heat-removal element 16, and (c) tominimize thermal loads on the device that are due to light absorptionfrom back-reflected or back-scattered light.

The mixer 12 comprises a hollow chamber where the wall material iseither copper or aluminum. The walls are either the polished substrateor coated to achieve high reflectivity to 800 nm light. The length ofthe mixer is designed to provide good spatial uniformity of light on a1.times. 1 cm output window from two diode bars spaced 6 mm apart. Thewall thickness of the mixer is designed to provide good thermalconductivity between the output window 14 and heat removal element 16.For copper walls surrounding a 1.times. 1 cm output window, a wallthickness of about 2 mm is required to conduct about 8 W of averagepower to a thermal source 2 cm away with a 5 degree C. temperature rise.The volume and weight of the mixer is about 4 cm³ and 20 g. The thermalload on the mixer due to light absorption is less than 1 W. Analternative embodiment of the mixer 12 might include various shapes andmay comprise multiple elements to achieve the thermal link between theoutput window and the heat removal element and to achieve light mixingand low light absorption. The cross-sectional shape may be any of avariety of shapes (such as circular or rectangular) and may vary alongthe length of the mixer. Because the skin, or the diffuser, or the wallsof the mixer may remit light in a direction away from the skin, themixer may comprise not only low-absorbing side walls, but also alow-absorbing surface opposite the output aperture. Such low-absorbingsurface may contain one or more openings through which light from thelight source passes, or may simply constitute the surface adjacent tothe light source.

In an alternative embodiment, the mixer may consist of an inner mixer,such as a sheet of polished metal, for the purpose of reflecting lightfrom the light source toward the output window 14; and a thicker metalouter surface, such as a copper or aluminum barrel, to conduct heat fromoutput window 14 to heat-removal element 16. In this embodiment, theinner mixer may alternatively be fabricated from a solid transparentmaterial such as glass or acrylic. In this case the light from the lightsource would be reflected toward the output window 14 by total internalreflection within the glass or acrylic.

Optical Diffuser

The term “diffuser” or “optical diffuser” refers throughout this patentapplication not only to conventional, commonly known elements such asthe “optical disk diffuser” of the flashed opal type (e.g., OrielInstruments Model 48010, Stratford, Conn.) but more generally to anyelement that, when incorporated into a light-emitting device having agiven radiant exposure or fluence, greatly reduces the integratedradiance (“brightness”) of the device. A diffuser generally increasesthe divergence and reduces the spatial coherence of light incident uponit.

With reference to FIG. 2A, diffuser 120 may be made of a material thatscatters light as it travels through it such the abovementioned opticaldisk diffuser from Oriel. Alternatively, diffuser 120 may be atransparent substrate whose surface has been roughened so as to scatterthe incident light through refraction. Diffuser 120 may be a bulkscattering diffuser, made for example from opal glass, PTFE, a thin(e.g. 0.5 mm) sheet of Spectralon, or combinations thereof. The diffuser120 may alternatively have a refractive or diffractive surface or body;or have a diffusing surface comprising random surface irregularities.Such diffusers may be made of ground glass, sandblasted glass orplastic, or molded materials produced by a randomly textured mold, orcombinations thereof. Alternatively, diffuser 120 may have a patternedsurface or body, for example with a holographic or Fresnel pattern.

The reflective diffuser 125 as shown in FIG. 2B may be constructed of ahighly scattering material such as PTFE, or a commercial material suchas Spectralon (available from LabSphere, Inc.). Alternatively, diffuser125 may comprise a scattering material such as Duraflect (also availablefrom LabSphere, Inc.) applied to the surface of the chamber 115 oppositethe skin 155. Alternatively, diffuser 125 may be fabricated simply byroughening the surface of chamber 115 opposite the skin 155; however,the preferred embodiment would incorporate an actual diffusing materialsuch as Spectralon, or an applied surface coating such as Duraflect, dueto the low absorption of these materials. Alternatively, diffuser 125may be made of a material that scatters light as it travels through itsuch as an opalized glass substrate, e.g., part #48010 manufactured bySpectra-Physics (Oriel), and then backed by a highly reflective mirror;in this way a transmissive diffuser material can be made to serve as areflective diffuser.

FIG. 3A illustrates an example of a diffuser 120 including transparentscreens of the fine-structure or lenticular types. FIG. 3A illustratestransmissive sheets having molded or machined refractive or diffractiveelements. The diffuser 120 may also include zones of concentricmicrogrooves, as illustrated at FIG. 3B.

The diffuser 125 of FIG. 2B may include merely roughened interiorsurfaces of a passageway through which light is scattered prior toexiting the device, such as illustrated at FIG. 3C, discussed inreference to FIG. 3E in more detail below.

Yet another means of achieving very low integrated radiance for a givenoutput fluence from a device in accordance with embodiments of theinvention includes a small light source approximating a “point source”projecting into a mixer having mirrored walls such as that illustratedat FIG. 3D.

FIG. 3E shows an embodiment of the current invention in contact withskin 250 that incorporates the use of the diffusing surface 220 of FIG.3C which the light strikes before leaving the apparatus though outputwindow 200. Again, light source 240 is housed within source chamber 230.However, instead of a diffusing material through which the light passesprior to leaving the device, a diffusing surface 220 is positionedrelative to source 240 such that the light strikes surface 220 prior toleaving the device. Diffusing surface 220 may be merely a roughenedsurface such as sand-blasted aluminum designed to diffuse the light, ordiffusing surface 220 may be a surface coated with a bulk diffuser suchas an opalized material used in part #48010 manufactured bySpectra-Physics (Oriel). Surface 220 need not coat the entire inner wallof source chamber 230 but only a sufficient portion to achieve a desiredlevel of beam divergence and reduced spatial coherence. A preferredembodiment would use a material for surface 220 that is substantiallynon-absorbing at the therapeutic wavelengths emitted by source 240.

Other designs are possible as understood by those skilled in the art andas provided in the literature incorporated by reference herein, i.e.,these are merely examples.

Output Window

The output window 14 is preferably a transparent, high heat capacity andhigh thermal diffusivity material, such as sapphire, with a low thermalresistance connection to the mixer 12. A thickness of 5 mm providesacceptable heat sinking capability for a 1.times. 1 cm sapphire window.The volume and weight of the output window 14 is about 0.5 cm³ and 2 g.The thermal load on the output window is about 8-9 W of average power.

Heat Removal Element

The heat-removal element 16 could be a thermal battery made of a highheat-capacity single-phase material, such as copper, water, or aluminum,or could be any of a variety of phase-change materials such as salthydrates and paraffin waxes, which can provide 5-10 times greaterthermal energy density and thus provide for a more compact thermalbattery. An embodiment with the thermal battery material TEAP/ClimatorClimSel 24 can store 210 J/cm³ and 144 kJ/kg over a 10 degree C. workingrange. Thus, for a 10 minute treatment at 23 W of average heat load thethermal battery would be about 70 cm³ and 100 g.

Alternative embodiments of the heat-removal element 16 include athermoelectric-based heat exchanger. The heat exchanger would have acold-side heat sink thermally connected to the rest of the device, athermoelectric module, and a hot-side heat sink thermally connected tothe environment. A fan to provide forced convection may be part of thisheat exchanger.

Additional Details of a Preferred Second Embodiment

A semi-schematic cross-sectional drawing of an apparatus in accordancewith a preferred second embodiment is shown in FIG. 10. Mounted at theend of device housing 610, which also serves as a handle, is the laserhead of the device, containing preferably two AlGaAs laser diode barsmounted on a fan-cooled, finned heat sink. The laser light propagatesthrough a square tube having a cross-section of 9 mm by 9 mm, through anopal-glass diffuser and sapphire window pair 626. The sapphire window,which is in contact with the skin during treatment, is held near roomtemperature by small thermoelectric modules mounted on either side ofthe diode bars.

A typical diode laser bar 500 including multiple diode emitters 510,such as that illustrated at FIG. 9 (and such as may be manufacturedbySpectra-Physics, Inc., of Mountain View, Calif., or Coherent, Inc., ofSanta Clara, Calif.), has a continuous optical power output of 20-40watts, and a maximum peak power output approaching 100 watts. For thisreason, a hair-regrowth-inhibition device with an output optical peakpower of over 25 W can be designed with only one or two bars 500, ratherthan 25 or more discrete laser diodes. Each laser diode bar 500 has manyindividual emitters 510 preferably fabricated on a monolithic structure,and requires roughly 40 amperes of current at a voltage of slightlyunder 2.0 volts to produce 30 watts of optical peak power output formore than 50 milliseconds.

Device housing 610 contains battery pack 710 consisting of, for example,six nickel-cadmium or nickel-metal-hydride 1.2 V “C size” batteries(e.g., Panasonic part no. P-170SCW, or HHR300SCP). Housing 610 alsoencloses circuit board 614 containing the control electronics, describedin detail below. Electrical power from the battery pack 710 isconditioned and controlled by electronics on circuit board 614, andcurrent of nominally 40 A is conducted through wires (not shown) tolaser diode bars 720 mounted on heat sink 618 (e.g., laser diode barpackages, part no. ASM06C040W080810B80, Cutting Edge Optronics).

Heat sink 618 is attached to finned heat sink 620 (e.g., part no.HX8-101, Melcor, Trenton, N.J.), and cooled by fan 622 (e.g., part no.FAN-101 from Melcor) which is also powered by the battery pack 710. Heatsink 618 is preferably a good thermal conductor and an electricalinsulator. The material BeO is preferably used for the heat sink 618.The finned heat sink 620 may comprise a block of aluminum or copper orother material of high thermal conductivity. The finned heat sink 620exchanges heat with the air which is circulated by fan 622. Laser lightfrom laser diode bars 720 passes through mixer 624 (for example, ahollow tube of square cross-section having highly reflective walls, suchas gold-plated aluminum).

Light from mixer 624 then passes through diffuser/window 626, preferablyof opalized glass (e.g., part no. W13.50 from Swiss Jewel) and sapphire,and subsequently passes into the person's skin 628 containing one ormore unwanted hairs. Diffuser/window 626 is prevented from overheatingby allowing excess heat from diffuser/window 626 to be conducted throughmixer 624 to the cold side of thermo-electric (TE) cooling modules 630(e.g., Melcor part no. CP 0.8-31-06L). TE modules 630 are in turn cooledby placement of their hot side against heat sink 620. TE modules 630 arepreferably solid-state devices that pump heat from mixer 624 to the heatsink 620.

The principal optical axis of the laser diode bars may be aligned withthe principal optical axis of the mixer and parallel to the normal tothe surface of the diffuser/window 626, as shown in FIG. 10. In anadvantageous embodiment, however, the principal optical axis of thelight emitted from the laser diode bars is not substantially parallel tothe normal of the surface of the diffuser. This may be accomplished bytilting the principal optical axis of the laser diode bars so that theyare not parallel to the normal of the surface of the output window; orby mounting the diode bars so that their principal optical axis isparallel to the normal of the surface of the diffuser, but the lightemitted from such bars strikes the diffuser at a different angle throughthe use of a mirror or mirrors. The angle is preferably around 45degrees. This embodiment permits the light generated by the laser diodebars 720 to already be spreading outward from the forward directionprior to striking the diffuser/window 626, resulting in an even morediffused and eye-safe beam propagated from the housing 410.

Electrical Circuit Design

Laser Diode Circuit Overview

An apparatus and method is described for dermatologic treatment in anembodiment that utilizes battery-powered laser diode bars. The apparatuscomprises a hand-held treatment device for dermatologic use, one or morebatteries, one or more laser diode bars, and an electronic controlcircuit. The apparatus enables, for the first time, effective homehair-regrowth inhibition, in a device significantly above the 1 Woptical output level that is compact, affordable (less than $1,000) andis free of cords and/or other connections to an electrical outlet. Thedevice incorporates a small number of batteries (preferably three tosix), an efficient circuit design that effectively draws 40 amperes ormore from the batteries, and typically contains one or two laser diodebars producing a combined optical peak power output of 10-120 W, or morepreferably 30-60 W, at 800 nm. With this apparatus, the consumer caninhibit hair regrowth in the privacy of the home using a device that hasan output power much higher than existing home “hair removal” devices(enabling more effective hair-regrowth inhibition and a faster coveragerate) while also enjoying the convenience of compact device size andcordless (battery-powered) operation. The device may also be suited foruse while plugged in, e.g., when it is not inconvenient to utilize thedevice while it is attached to an outlet or other source of electricalpower. This can save battery power at times and can also serve torecharge the batteries.

The concept is not limited in its advantageous application tohair-regrowth inhibition, nor to the preferred wavelength ofapproximately 800 nm; but rather, may be applied more broadly todermatologic treatment utilizing battery-powered laser diode bars forother applications, and/or other wavelengths. For example, benignpigmented lesions and unwanted leg veins may be treated bydermatologists in an office setting using an 800-nm laser diode barsource; and treatment of acne by destruction of the sebaceous gland ispossible utilizing a similar laser diode bar source at 1400 or 1700 nm(both absorption peaks of sebum). The invention is also not limited todevices containing only one or two laser diode bars each containingmultiple laser diode emitters, but may include a different number oflaser diode bars and may include other alternative light sources such assolid-state lasers, semiconductor lasers, VCSEL's and flashlamps, amongothers that may be understood to those skilled in the art that generallymeet the input and output criteria described herein for abattery-powered, home care device.

An apparatus and method in accordance with a preferred embodimentinclude increased eye safety by increasing the divergence and reducingthe spatial coherence of the light emitted from the output aperture ofthe dermatological apparatus. It is noted that the output aperture maybe a clipping aperture, but as used herein, is not so limited, and theterm is meant to include any plane through which the light travels ortransmits, and may comprise a particular solid material such as a windowor optical diffuser or a fluid such as air.

The apparatus and method may alternatively involve operation from aconventional wall outlet, eliminating the need for batteries.

Overview of Batteries and Control Electronics

Although a transformer can in principle be used to increase the 0.001-3amperes typically drawn from batteries to the 40 ampere level, thisapproach is impractical in the home device application described for tworeasons. First, incorporation of a suitable transformer adds weight,volume and cost; and secondly, a step-up in current via a transformernecessarily is accompanied by a corresponding step-down in voltage.Thus, for example, a transformer that converts 2 A at the input to 40 Aand 2 V at the output has a turns ratio of 20:1, and thus utilizes aninput voltage of 40 V. Since batteries are typically 1.2-1.5 V output,either many batteries (greater than 25), or voltage boost circuitrywould likely be employed. These complexities add further to the weight,size and cost of the device. Alternatively, one might consider theaddition of a “supercapacitor” (i.e. a high-capacitance electricalcomponent that has recently become commercially available, termed anUltraCapacitor by Maxwell, Inc. of San Diego, Calif.) with a capacitanceof 1 farad or more. This device can provide very high current, butunlike a battery its output voltage decreases rapidly at constantcurrent output, in addition to adding its own weight and volume.

The handle of the preferred apparatus contains a rechargeable batterypack containing five “sub-C” size nickel-metal-hydride or similarbatteries, capable of powering the device without a main storagecapacitor or transformer for approximately 300-500 pulses betweenrecharges. That is, the circuit of the preferred embodiment is a “directdrive” electrical circuit wherein the current flowing from the batteriesduring a light pulse is substantially equal to the current flowingthrough the light source, or is substantially equal to the sum of thecurrents flowing in parallel through multiple light sources. The voltageprovided by the batteries will not be substantially greater than thevoltage applied to the light source due to small voltage drops atvarious resistances in the circuit.

The electrical battery serves as the source of electrical power in apreferred embodiment. The electrical battery could be comprised of (a) abattery that drives the light source directly, which is the preferreddirect-drive electrical circuit, or alternatively (b) a battery thatcharges a supercapacitor that drives the light source, (c) a batterythat charges a capacitor that drives the light source, (d) asupercapacitor that drives the light source directly, or (e) asupercapacitor that charges a capacitor that drives the light source.The chemical battery may be non-rechargeable, such as alkaline, orre-chargeable, such as nickel-metal hydride (Ni—MH). A rechargeablebattery would provide greater convenience and lower cost for the user.For topology regarding the alternative embodiment (c), a Ni—MH batteryof about 50 cm³ and 170 g would provide for about 15 minutes ofoperation. The capacitor would be about 50 cm³ and 50 g.

Nickel-metal-hydride batteries are preferred over Li-ion batteries,which have substantially lower peak current capabilities. Ni—Cdbatteries have undesirably low energy densities, although they do havelower series resistances. The Ni—MH batteries selected have a batterycapacity of 3 Ampere-hours (Ah) at a voltage of 1.25 V and can easilygenerate the 500 pulses. These batteries are preferably andadvantageously factory installed. That is, they are preferably onlyreplaceable at the factory (e.g., during a refurbishment). Analternative consumer-replaceable battery embodiment, either disposableor rechargeable, involves a more complex design and higher cost. Such analternative would involve battery contacts rather than soldered wires,and since the circuit of the preferred embodiment drives approximately40 A, even 25 milliohms of contact resistance results in a one volt dropwhich is very undesirable in that it represents a considerable fractionof the total battery voltage available. Soldered battery contacts, whichare preferred, have much lower resistance.

Electrical Circuit Details

FIG. 11 shows the salient features of an electrical circuit inaccordance with a preferred embodiment. Incidental components have beenlumped into the various blocks of the circuit diagram. Although detailwithin each of the blocks is not shown, it is submitted that thoseskilled in the art can implement each of the blocks. The electricalcircuit for powering and controlling the hair-regrowth-inhibitionapparatus of the preferred embodiment is advantageously robust andefficient in driving a pair of laser diode bars within a cordless,hand-held, and self-contained device. The details of control electronicscan vary greatly from the description below, and as schematicallyillustrated by the block diagram in FIG. 11, and as shown in some moredetail in FIG. 12 in accordance with a preferred and exemplaryembodiment.

The controller of the device is the processor 888. Contained within theprocessor block is a microcontroller such as a PIC18LF452, manufacturedby Microchip Technologies of Chandler, Ariz. Such a controller has manyanalog I/O, digital I/O, onboard read access memory (RAM), nonvolatilememory (FLASH and EEPROM), and other features that make it inexpensive,small and convenient to use in a self-contained device that isrelatively small and lightweight compared with conventional office-baseddevices. Although the device does not need to employ the use of amicrocontroller, using one makes the capabilities of the device greaterthan it would be otherwise possible for a given size. Alternatively, itmay be possible to use a custom application-specific integrated circuit(ASIC) for the processor and much of the other electronics. The triggerbutton 826 is used by the operator of the device to signal that atreatment pulse is desired. A trigger switch 826 may be omitted if thecontact sensors 819 and 820 are used as a means to signal that theoperator desires a treatment pulse. The processor 888 communicates withthe other blocks through various signals. The processor may communicatewith peripheral devices through a serial interface port 836. Theprocessor may also have a programming port 837 by which themicrocontroller may be programmed while preferably already soldered intothe circuit. The programming port 837 may also be used with anin-circuit-debugger (ICD) to make design and debugging of the softwaremore convenient.

A device in accordance with a preferred embodiment is powered by batterypack 806 and DC/DC converter 887. The number of batteries in the batterypack are sufficient to drive current through the laser diodes 800, orLED, flashlamp or other alternative light source, current senseresistors 801 and 804, and FET's 802 and 803. With great attention toparasitic resistances and creative circuit architecture, the preferredbattery configuration includes five batteries rated at 1.2 V each andproviding between 1.0 V and 1.5 V during the course of a dischargeperiod. The voltage provided by the battery pack 806 is then between 5.0V and 7.5 V.

The DC/DC converter 887 monitors the power button 825, a wake-up signal838 from the battery charger 886, and a shutdown signal from theprocessor 888. The DC/DC converter 887 signals the processor 888 if thepower button 825 is depressed via the power switch signal 834. A signalproportional to the battery voltage is communicated by the DC/DCconverter 887 to the analog conditioning electronics 889 via the batteryvoltage monitor signal 827. The DC/DC converter 887 produces the variousvoltage levels required to power the other blocks of the circuit, namelya reference voltage 828, FET gate drive voltage 829, electronics supplyvoltage 830, and a switched battery voltage 831 that can be switched onand off by the DC/DC converter 887. The blocks in the diagram shown inFIG. 11 preferably each have a connection to the signal common 807 whichmay or may not be shown. Since any switch between the battery and othercomponents would develop a parasitic voltage drop, the battery packvoltage provided to the laser diode loop is not switched independent ofthe sentinel FET(s) 802 and control FET's 803. The absence of a switchis shown via the battery signal 805.

The battery charger 886 is used to charge the battery pack 806. Acommonly available low power, 9 VDC, 500 mA power adapter (not shown)can be connected at the DC power jack 824. The battery charger 886 has afast-charge mode that charges the battery pack 806 with a current ofabout 450 mA and a trickle-charge mode that charges the battery pack 806with a current of about 30 mA. The battery charge mode may be selectedby the processor 888 via the fast charge signal 839. The processor isinformed of the charge state of the battery pack via one of the signalsin the analog signal bus 841. When a DC adapter is connected to the DCpower jack 824, the battery charger can signal the DC/DC converter 887to wake up via the wake-up signal 836 and can signal the processor 888via the charge voltage monitor signal 840. Because the processor knowsof the presence of the power adapter and the charge state of thebatteries, an intelligent algorithm may be used for fast recharging ofthe batteries 806.

The analog conditioning circuitry 889 amplifies and converts the signalimpedance, where necessary, of the various analog voltages that are sentto the processor 888. These signals include the laser diode cathodevoltage 813, the current sense signal 814, the battery voltage 827, skinsensor detector signal 842, reference voltage 828, and voltagesrepresentative of the temperatures sensors 850, 851, and 852. Thetemperature sensors may be used to monitor the voltage of the finnedheat exchanger; the cold side of the thermoelectric cooler elements 858;and the battery pack 806 and main circuit board. The conditioned analogsignals are conveyed to the processor over the analog signal bus 841.

The purpose of the skin sensor circuitry 890 is to distinguish thepresence of skin from other materials at the output aperture of thedevice. Light emitting diodes (LED's) 853 and 854 are used to illuminatethe output aperture of the device. Remitted light is sensed by detectors855 and 856. The processor 888 may select which LED to illuminate viaaddress bus 843. The signal from detectors 855 and 856 are summed andcommunicated to the analog conditioning electronics 889 via the detectorsignal 842. The processor 888 can then compare the detector signal foreach LED against the known expected value for skin. In this way, skincan be distinguished from many other materials. In a preferredembodiment, five LED's, emitting light in the blue, green, yellow, red,and infrared portions of the electromagnetic spectrum are used. Simplesilicon phototransistors are used to detect the remitted light. Greateror fewer LED's may be used to increase or decrease, respectively, thedegree to which the skin sensor can reliably distinguish between skinand other materials.

The fan and TE module electronics 891 provide power to the fan 857 andTE module 858. A fan signal 844 and TE module signal 845 from theprocessor 888 determine if the fan and TE module electronics 891 providepower to the fan 857 and TE module 858, respectively.

Visual indicators used to communicate with the operator include threeLED's, power 859, ready 860, and battery 861. An audible indicator 862is also preferably used to provide user feedback. The audible indicatoris especially advantageous on a self-contained device since the operatormay have difficulty seeing the device if used for self-treatment ofareas of the body that do not enable the direct view of the visualindicators 859, 860, and 861. The power indicator 859 is used to signalto a person that the device is on. The ready indicator 860 signals thatthe device has initialized, is at the proper operating temperature, andthat the user may begin treatment. The battery indicator 861 signals thecharge state of the battery. All three indicators may be steadilyilluminated (in addition to other preferred conditions) for the deviceto emit a treatment light pulse. The speaker 862 may be used to indicatepower on, power off, a treatment pulse, and/or many other events throughthe use of different tones and various tone sequences and durations.Each of these indicators has an associated control signal from theprocessor 888: speaker signal 846, battery signal 847, ready signal 848,and power signal 849.

The contact sensor electronics 880 are used to detect contact of theoutput aperture and/or output window component of the device with a firmsurface such as skin. One or more sensors, 819 and 820, may be used tosense contact of different portions of the output aperture. Three simplecontact closures implemented through the use of a membrane switchcommonly found in cell phone keypads, calculator keypads, or otherelectronics are used to detect contact in the device of the preferredembodiment. Other contact sensors using light, ultrasound, electricalresistively or other physical phenomena may be used. The state of thecontact sensors are communicated to the processor 888 via the contactbus 821. The processor may use a complex algorithm for determining ifsufficient contact is provided before it signals the other controlelectronics that a treatment pulse may be initiated and maintained. Thecontact sensor electronics 880 also may directly (and redundantly)signal the pulse enabling electronics 881 via a contact signal 815.

The current control electronics 885 provide closed-loop control of thecurrent flowing through the laser diodes 800. The differential voltageacross current sense resistor 1 (804) is monitored by the currentcontrol electronics 885 and is proportional to the current flowingthrough the laser diodes 800. This differential voltage is amplified andcompared to a set point voltage that can be adjusted by the currentsetpoint resistor 812. The voltage on the gate of the control FET's 803is continuously adjusted by the current control electronics 885 toensure that the proper current is flowing. When no treatment pulse isdesired, as indicated by the pulse not signal 823, the current controlelectronics 885 turns off the control FET's 803.

The current limit electronics 884 are used to monitor the currentflowing through current sense resistor 2 (801). In a similar fashion asthe current control electronics 885, the current limit electronics 884amplifies the differential voltage developed across current senseresistor 2 (801) and compares this voltage with a voltage set by currentlimit resistor 811. If the current flowing through current senseresistor 2 (801) exceeds the limit, then an over-current error issignaled to both the pulse enable electronics 881 and the processor 888via the over-current error not signal 810.

The pulsewidth limit electronics 882 are used to monitor the pulsewidthof the treatment pulse. An independent time base (different from thatused by the processor 888) is used to ensure the duration of anytreatment pulse does not exceed a time set by the pulsewidth limitresistor 817. If the processor 888 requests a pulse via the pulse notsignal 823 that exceeds the pulsewidth limit then the pulsewidth limitcircuitry 882 signals the processor 888 and pulse enable electronics 881via the pulse width error not signal 818.

The pulse rate frequency (PRF, or repetition rate) limiting electronics883 are used to ensure that treatment pulses are not emitted morefrequently than desired. If sufficient time is not allowed by theprocessor 888 between pulses requested on the pulse not signal 823, thenthe PRF limiting electronics 883 indicates an error to the pulseenabling electronics 881 via the PRF limit not signal 816.

The pulse enabling electronics 881 ensure signals from other blocksindicate that the other blocks have satisfied their requirements priorto the initiation of a treatment pulse. These signals may include:contact 815, no over-current condition 810, no pulsewidth errorcondition 818, no pulse rate frequency (PRF) error 816, and the presenceof a processor enable signal 822. If all of these enable signals arepresent, the pulse enable electronics 881 turns on the gate of thesentinel FET's 802 via a sentinel gate signal 809. If at any time any ofthe signals that are monitored by the pulse enabling electronics 881indicate that the pulse should not continue, the sentinel FET's 802 areturned off by the pulse enabling electronics 881 and the output may beterminated mid-pulse.

The laser energizing circuit loop is shown comprised of the followingelements: the laser diodes 800, battery pack 806, current sense resistor1 (804), current sense control FET's 803, sentinel FET's 802, andcurrent sense resistor 2 (801). This loop is shown in more detail inFIG. 12.

FIG. 12 shows the detailed schematics of the circuitry used to controlthe current to the laser diode bars. As indicated in FIG. 12, thebattery pack 806 positive and negative electrodes are be connected atterminals J4 and J2, respectively. The laser diode bar cathode and anodeare connected at terminals J1 and J3, respectively. Current senseresistor 1, R1, and current sense resistor 2, R2, are shown as 0.002 ohmresistors. The current control FET's are shown as a parallel connectionof two FET's Q2 and Q4. The sentinel FET's are shown as a parallelconnection of two FET's, Q1 and Q3. Resistors R3, R4, R5, and R6 are apart of the control electronics not shown discretely in the blockdiagram of FIG. 11. Resistors R3 and R4 are connected to the gates ofthe sentinel FET's and current control FET's, respectively, so that thetransistors turn off if either gate signal is for some reasondisconnected. R5 and R6 are used to generate the laser diode cathodevoltage signal 813 of FIG. 11. The capacitors C1, C2, C3, and C4 areused to reduce the switching noise of the FET's and may not benecessary.

FIG. 11 and FIG. 12 show the salient features of an electrical circuitthat can be used in accordance with a preferred embodiment. Anadvantageous feature of the design illustrated in FIG. 11 and FIG. 12 isthat the laser diodes are powered directly by the battery pack. Here,the phrase, “powered directly,” or, as used elsewhere herein, thephrase, “direct drive,” are intended to mean that the instantaneouscurrent flowing through the battery and the instantaneous currentflowing through the laser diodes at a particular moment in time aresubstantially equivalent. The instantaneous currents differ only in thata small amount of current drawn from the batteries is used to power thecontrol electronics. This architecture is markedly different from andadvantageous over state-of-the-art laser systems and flashlamp systemsused for hair-regrowth inhibition due to various efficiencies that itprovides.

Efficient Electrical Circuit Design

There is significant architectural advantage in the circuit of FIGS. 11and 12 over conventional pulse power circuits for delivering 40 amperecurrent pulses for energizing pulsed laser systems. Most circuits thatare capable of delivering large current pulses rely on a main storagecapacitor to store the electrical charge that is to be delivered duringthe pulse. For example, state-of-the-art hair removal systems like theLightSheer diode laser system, the Quantum flashed lamp system, and theAltus CoolGlide all have large banks of capacitors that are re-chargedby a DC power source between pulses. In contrast, the system of thepreferred embodiment includes a direct drive electrical circuit. Asdescribed above, the circuit directly switches current pulses from thebatteries to the laser electrodes and does not include a main storagecapacitor. Such main storage capacitor would involve a large bank ofcapacitors due to the low energy density of capacitors. Moreover,preferably no step-up or step-down transformer is used in the directdrive electrical circuit. This permits the size and weight of theapparatus of the preferred embodiment to be significantly less than acircuit including a main storage capacitor and/or transformer; and so inaccordance with one of the goals of the design of the preferredembodiment, the additional size and weight of a main storage capacitorbank and transformer are avoided.

In addition, in capacitor-based systems, as current is delivered by acapacitor bank the stored charge decreases, and the voltage across thecapacitors drops significantly (voltage=charge/capacitance). The drop involtage means that the initial DC voltage would need to be larger thandesired so that there would be sufficient voltage available to continueto drive the system as the capacitors discharge. Thus, greater wastepower would be generated across the control FET's 803 during thebeginning of the pulse when the voltages have not dropped significantly.This would be inconsistent with the desire to have an energy-efficientcircuit for the hand-held, cordless apparatus of the preferredembodiment. Further size and weight advantages are achieved in thedirect drive electrical circuit of the preferred embodiment by avoidinguse of a transformer.

Advantageous to the efficient use of power of this device is the use oflaser diode bars 800. In FIG. 11, the symbol for a single diode is usedto represent the series connection of one or more, and preferably two,laser diode bars. Laser diodes are much more efficient at convertingelectrical power to optical power than other lasers. In the preferredembodiment, two laser diode bars are connected in series. Laser diode800 can be 40-watt, 808-nm packages manufactured by Cutting EdgeOptronics, of St. Charles, Mo., part number ASM06C040W080810B80 orsimilarly packaged laser diode bars 800. A single diode bar 800 may beused if the optical power delivered is sufficient for therapeuticresults. However, an efficient laser source is preferably combined withefficient batteries and circuit design in order to realize aself-contained and hand-held hair-regrowth-inhibition device.

Therefore, in the circuit of the preferred embodiment, the size of thebatteries and the electrical circuit configuration are such that mainstorage capacitors are not required. Instead, the laser diodes aredriven “directly” from the DC power source, or the battery pack. Theusable voltage of the battery pack is reduced by the product of thecurrent and the equivalent series resistance of the batteries(voltage=current.times.−resistance), and so the batteries includeadvantageously small series resistances. Also, the batteries are capableof supplying approximately 40 A without damage. Although the most recentbattery technology is lithium-ion, nickel-metal hydride oralternatively, nickel-cadmium, are preferred, because the maximum peakcurrent draw is much greater than Li-ion can provide, for a givenbattery size. The choice of battery within battery pack 806 is stronglydriven by its equivalent series resistance, or ESR. When drawing largecurrents from a battery, significant voltage can develop across thisparasitic resistance. The voltage developed due to ESR is subtractedfrom the nominal battery voltage and so reduces the voltage available tocircuits the battery is powering. The ESR is preferably low enough sothat, when 40 A is drawn from battery pack 806, the resulting parasiticvoltage drop is small compared to the voltage output of the battery pack806. The “compact C” Ni—MH batteries have been selected for these andother reasons already mentioned. The batteries that comprise batterypack 806 may be Panasonic HHR300SCP Ni—MH rechargables, PanasonicP-170SCRP NiCd batteries, sold by Panasonic Matsushita ElectricCorporation of America, Secaucus, N.J., or similar batteries.

Another advantage of the circuit design of the preferred embodiment isthat voltage drops are minimized and/or avoided in many places. In FIG.12, the laser diode bars are shown connected in series with the battery,FET's and current sense resistors. Minimizing the voltage developedacross the components powered by the batteries is advantageous becausethis will determine the minimum voltage and hence the minimum number ofbattery cells that are included in the design and thus in part establisha lower limit on the weight and size of the apparatus. Voltage dropsacross the FET's, the current sense resistors, the laser diodes, thebattery series resistance, and the circuit board traces and the otherinterconnections between these components have been taken intoconsideration.

The current sense resistors 804 and 801 are redundant current-senseresistors. The resistors are redundant for safety reasons. Each is usedby a different sub-circuit to ensure that currents larger than desiredare not permitted to flow through the laser diodes. Because of the largecurrents flowing through them (approximately 40 A each), an appreciablevoltage will develop with even a small value of resistance. For thisreason, components that are commonly thought of as resistors are notused, and instead, merely 1.5 inch lengths of 22 gauge copper wire areused. These lengths of wire have a resistance of only approximately0.002 ohms, so that a voltage of approximately 80 mV develops acrosseach of them when the laser is pulsed. Differential amplifiers withinthe current control electronics 885 and current limit electronics 884serve to amplify the voltages to levels that are more readily used bythe feedback circuitry.

The control FET's 803 are the FET's that control the current flowing inthe circuit. Any excess voltage supplied by the batteries, that is,voltage greater than that involved in driving the desired currentthrough the laser diodes, is dropped across the control FET's 803.However, as the batteries are discharged and the battery voltagedecreases, there will not be excess voltage supplied by the battery, andso the voltage that develops across the FET's for the case when thebatteries are nearly depleted is advantageously minimized in accordancewith a preferred embodiment, because the FET's chosen have very lowon-resistance (r_(ds-on)). The transistors shown, IRL3716 (InternationalRectifier Corp., El Segundo, Calif.), are actually 180 A/200 Wtransistors and are larger than are needed for merely current and powerrequirements. However, their low on-resistance is advantageous for thisapplication. In addition, to lower the voltage developed across theFET's, two transistors in parallel are preferred instead of just one sothat only approximately 20 A flows through each transistor.

The sentinel FET's 802 are used to shut off the current if an errorcondition exists (for example, if one of the control FET's 803 fail suchthat current flows when it should not). The sentinel FET's 802 arechosen with preferably the same criteria as the control FET's 803 withone exception. Since the sentinel FET's 802 are used only digitally topermit any current set by the control FET's 803 or restrict any current,the FET's are either turned on “hard” or else turned off completely. Inboth of these states, little power is dissipated by the sentinel FET's802 and so the transistor's packaging can have worse thermal performancethan the packaging of the control FET's 803. For this reason, in FIG.12, transistors such as IRF7832 (International Rectifier Corp.) may beused for transistors Q1 and Q3. IRL3716 transistors would be acceptablefor use as FET's 802; however, they would undesirably add to the size,cost, and weight of the device.

The series resistance of the FET's is further reduced by enabling thecircuit to supply relatively high voltages to the gates of each of thetransistors. The on-resistance of FET's sharply depends inversely on themagnitude of gate-to-source voltage applied to the device. The DC/DCconverter electronics 887 in FIG. 11 produce an FET gate drive voltage829. In the preferred embodiment the gate drive voltage 829 produced bythe DC/DC converter is 7.6 volts even when the battery pack voltagedrops to less than 5 volts. This voltage is greater than the batterypack voltage and is present so that the FET gate-to-source voltage, Vgs,of each of the FET's can be driven to a greater value than would bepossible if the magnitude of the voltage was limited by the battery packvoltage. This is especially true as the batteries become depleted andthe battery voltage decreases to less than its fully charged level.

The control FET's 803 and sentinel FET's 802 are located in a way thatminimizes the length of the traces and interconnects, isolates thecurrent paths from sensitive circuitry, and provides a means ofconductively rejecting the waste heat produced by the transistors to thefinned heat exchanger 620 of FIG. 10. Wide, short traces and redundanttraces on multi-layer boards achieve this. In a preferred embodiment,conventional electrical connectors are not used in the high current pathso as to eliminate connector resistances. Instead, components aresoldered at the factory. This represents a trade-off between ease ofmanufacture and repair with reductions in voltage drops throughout thecircuit, wherein even milliohm parasitic resistances are avoidedwherever possible.

Optical Parameters

Optical Output Specifications

Although particular output specifications for light pulses emitted fromthe apparatus of the preferred embodiment will be explained in moredetail below, an exemplary device in accordance with a preferredembodiment may produce light pulses according to the following summaryof parameters:

Output fluence: 18 J/cm²

Spot size (or output aperture area): 1 cm²

Pulsewidth: 0.300 s

Pulse repetition frequency: 0.5 Hz

Wavelength: 808 nm

Therefore, the peak optical power is 60 W and coverage rate is 30 cm²per minute. These provide efficacious and practical treatmentspecifications. As will also be detailed below, these particularparameters fall within ranges for minimum and maximum quantities for thepreferred device. These ranges preferably include:

Output fluence range: 4 J/cm² to 100 J/cm²

Spot size (or output aperture area): 0.25 cm² to 2 cm²

Pulsewidth: 0.010 s to 1 s, or more preferably 0.100 s to 0.500 s

Pulse repetition frequency: 0.1 Hz to 2 Hz

Wavelength: 700 nm to 1100 nm

Optical Peak Power (Peak Power): 10 W to 120 W.

Output Fluence

Throughout this patent application the term output fluence is intendedto describe the fluence at the output aperture or output window of thedermatologic treatment apparatus. For purposes of clarification, theoutput fluence of the device is also termed below as F_(source).

Among the most important output parameters, it is generally preferred tohave a source fluence F_(source) between 4 J/cm² and 100 J/cm². Forpulse durations in the 0.3 ms to 3 ms range, temporary hair regrowthinhibition has been found clinically with output fluences as low as 4-5J/cm². However, for pulse durations extending into the many tens tohundreds of milliseconds, it is believed that output fluences belowabout 10 J/cm² are unlikely to have significant effect. In the absenceof actual clinical trials at these parameters, it cannot be establishedmore precisely, and in any case will vary from person to person and evenwith body site on a single person.

Output fluences over approximately 100 J/cm² would be expensive toproduce, unless an undesirably small spot size or excessively long pulsewidth is utilized. In addition, if this fluence is exceeded in less than1000 ms, it is likely to be very painful or even cause burning of theskin. The fluence that the skin can tolerate is generally affected by atleast four parameters. The first is the extent to which the epidermis iskept from rising in temperature while the target below is heated. Inthis regard, the preferred device includes a thermally-conductivecontact surface made of sapphire, or alternatively incorporates someform of active cooling of the contact surface or the skin such as usinga fan. Alternatively, cryogen spray may be used to cool the skin to betreated.

As discussed above, the safety of a home device is enhanced with loweroutput fluences. Further, higher output fluences, e.g., achieving twicethe fluence with a same spot size involves twice the number of laserdiode bars and probably twice the batteries. Thus the practical designconstraints of a self-contained, hand-held, cordless, self-care deviceon safety, weight, size, and cost suggest that output fluences less thanabout 100 J/cm² are desired.

The laser diode bars of the light source 140 preferably emit lightpulses such that a majority of the energy is in the spectral band of 700nm to 1100 nm, and particularly around 800 nm, although visiblewavelengths may also be used; bandwidths between approximately 1 nm and10 nm; pulse durations preferably between 3-10 milliseconds (ms) and onesecond, and more preferably between 100 ms and 500 ms and particularlyaround 300 ms, at a repetition rate of between 0.1 Hz and 2 Hz, andparticularly between 0.25 Hz and 1 Hz.

Wavelength

Another significant parameter is the wavelength of the light. Ingeneral, the longer the wavelength, at least over a range between 400 nmand 1100 nm, the higher the fluence tolerated by the skin, because theabsorption of light by the melanin present in skin decreasesmonotonically with increasing wavelength over this range.

In a hair-regrowth-inhibition procedure, melanin in the hair shaft andfollicle absorbs light, resulting in thermal injury to the follicle anddelayed regrowth. Thus one might assume that light having a shorterwavelength would be preferred, since these wavelengths are more stronglyabsorbed. However, the melanin in the skin overlying the hair folliclealso absorbs more light at these wavelengths, reducing the fluencetolerated by the skin. Theoretical calculations and clinical resultshave determined that optimum results for hair-regrowth inhibition areobtained for most skin types when the light source has an output in thespectral band between 700 nm and 1100 nm. Wavelengths longer than 1100nm, in addition to having very low melanin absorption, also becomeproblematic due to water absorption, which begins to limit opticalpenetration depth making the apparatus less efficient.

The preferred wavelength of emission of the light source 140, preferablymade up of one or more laser diode bars, is thus between approximately700 nm and 1100 nm. In the case where a flashlamp is utilized as thelight source, particularly for other dermatologic procedures, awavelength of 500 nm to 1100 nm may be preferred, since flashlamps areinherently broadband sources, and thus a broader wavelength range may beinvolved for achieving the desired fluence.

In addition, if blood vessels are targeted, the increased absorption ofblood at wavelengths in the region of 510-580 nm make somewhat shorterwavelengths desirable.

In the case where LED's are utilized as the light source, higher powerLED's may be available at wavelengths below 700 nm; thus a wavelengthrange of 600 nm to 1100 nm may be preferred.

Bandwidth

The pulses emitted by the light source 140 are generated preferably byenergizing the laser diode bars with 40 A for less than half a second.Therefore during the application of this energy, the laser diodematerial warms from about 20.degree. C. to about 50.degree. C., or adifference of 30.degree. C. over the duration of the pulse. The emissionwavelength particularly of III-V emitter materials such asAI_(x)Ga_(1-x)As varies with temperature. For example, A(T) may vary byabout 0.3 nm/.degree. C. Therefore, the emission wavelength may vary byabout 9 nm during the pulse, and the effective bandwidth of the pulse isthen generally about 1 nm and may be between about 5 nm and 10 nm. Whereused herein, bandwidth is defined as the full-width half-maximum of theenergy spectrum.

Sources such as diode lasers or LED's, that typically have bandwidths ofless than 40 nm, are generally preferred over flashlamps because theyhave higher electrical-to-optical conversion efficiency.

Pulse Repetition Frequency

The repetition rate of pulses, or pulse repetition frequency, ispreferably between approximately 0.1 Hz and 2 Hz, and particularlybetween around 0.25 Hz and 1 Hz, or between one pulse every second toone pulse every four seconds. A repetition rate any faster than 1-2 Hzis not desired owing to the expense and weight of a device capable ofproducing pulses this rapidly. Moreover, the self-care user of thedevice, whether it is a person at home applying the light to his or herown skin, or a user treating another person's skin, would find itdifficult to manipulate the apparatus over the application area of theskin at higher repetition rates. On the other hand, a repetition rateslower than one pulse every four to ten seconds would render thecoverage rate of the apparatus annoyingly slow for home use. That is,the application time simply becomes too long even for small treatmentareas.

A higher repetition would translate into a higher coverage rate or moreskin area treated per minute, which is desirable. However, a higherrepetition rate also involves a higher average input power since theaverage optical power is higher. This higher electrical powerrequirement, in addition to increased volume, weight and cost, creates aproblem of waste heat from the laser diode bars of the preferredapparatus.

Pulse Duration

Another important parameter is pulse duration. If the epidermis is keptfrom rising excessively in temperature, the energy can be continued tobe applied into the hair follicle over a time that is roughly thethermal relaxation time of the stem cell region of the follicle, e.g.,for approximately 100 ms to 500 ms. With contact cooling, the epidermisis kept from getting too hot; and much more fluence, or energy over agiven area, can be applied into the dermis if it is applied over alonger time period.

The preferred pulse duration of the apparatus is above 3-10 ms and belowapproximately one second or even 500 ms. Pulse durations below around 10ms, and particularly below 3-8 ms, are not desired for the light-basedhair-regrowth-inhibiting apparatus, because to achieve adequate energydeposition in such a short time requires high optical peak powers. Forexample, application of an energy density of 20 J/cm² in a 0.8 cm² spotarea (16 J) in a 10 ms pulse involves a optical peak power of 1600 W.This very high peak power is expensive to generate. For example, withdiode laser bars each having a optical peak power of 30 W, over 50 barswould be used, and this is too many for a self-contained, hand-held andcordless device. It is also more difficult to render the deviceeye-safe, which is important in a home use, self-care device, becausethe maximum permissible exposure (MPE) is much less for short pulsessuch as these. That is, the MPE scales as the pulse duration to thethree-quarter power, or t^(0.75), and for eye safety, it is thereforegenerally more desirable to have longer pulses at desired outputfluences than short ones. The thermal relaxation time of the hairfollicle is generally at least 10 ms and may be as high as 100 ms to 600ms for the stem cells surrounding the hair follicle, and so for thereasons provided, it is particularly desired to have pulse durations atleast as long as this thermal relaxation time, such that a particularlypreferred minimum pulse duration may be 100 ms or more.

On the other hand, as pulse durations get too long, such as abovebetween 600 ms and one second, heat which is initially deposited intothe melanin-laden hair shaft diffuses beyond the hair follicle.Somewhere in this pulse duration regime a transition gradually occursfrom spatially-selective heating of just the follicle (and surroundingstem cells) to so-called bulk-heating of the dermis. If the pulseduration is increased at constant energy (or constant fluence), theoptical peak power eventually gets so low that the target does not getsufficiently hot to cause hair-regrowth inhibition. If the peak power iskept constant as the pulse duration is increased, the fluence can get sohigh that the bulk heating becomes painful and/or may even cause skinbums.

It is noted that use of the term pulse, or pulse duration, is intendedto include not only a single pulse in the conventional sense, but also atrain of discrete pulses (“sub-pulses”) or modulated pulse over the sametime duration. In general, for the purposes of this patent application,these sub-pulses are considered to be one pulse if the time durationbetween the start of the first sub-pulse and the end of the lastsub-pulse in a group is less than the time period between groups of suchsub-pulses.

Optical Peak Power

It would be difficult to effect even temporary hair-regrowth inhibition,e.g., temporary delay in hair regrowth, if the optical peak power of thelight source is below approximately 10 W. At peak powers below thisthreshold, very long pulse durations would be involved to approach alower limit on output fluence, e.g., 4 J/cm². For example, to get anoutput fluence of 10 J/cm² in a 0.8 cm² spot (i.e., and output energy of8 J) a pulse duration of 800 ms is required at a peak power of 10 W.

At peak powers of over approximately 100-120 W, considerable energy canbe generated in a pulse having a more desirable duration and a usefulspot size. However, higher peak powers are difficult to obtain in aninexpensive, self-contained, battery-powered self-care device.

Spot Size

There are multiple undesirable effects if the spot size, or area of skinilluminated by light pulses propagated from the apparatus, is too small.(In cases where the output aperture of the device is close to, or incontact with, the skin, the spot size on the skin and the outputaperture of the device are approximately equal in size.) First, a verysmall spot, e.g., less than 0.25 cm², renders only one hair to betreated at a time in a hair-regrowth-inhibition procedure. In addition,some sort of visual targeting would be involved to ensure that the spotis indeed over a target follicle. Second, a small spot implies a verylow coverage rate; i.e. to cover a given number of square centimeters ofskin containing unwanted hairs, the smaller the spot size the longer thetreatment time. This problem can be mitigated to some extent byincreasing the pulse repetition rate, but doing this involves moreelectrical power, more expense, and more weight. Third, while a smallspot size would appear to be quite advantageous in the sense that a lowenergy can still generate a high fluence on the skin surface (sincefluence is energy divided by area), the fluence at some depth within theskin where the target cells are located is substantially reduced byscattering within the skin. The smaller the spot size, especially belowabout 0.25 to 0.5 cm², the more pronounced the effective lessening offluence at depth relative to fluence at the surface. In short, if onegoes to too small a spot, the end result can be either burning of theepidermis (to get enough fluence in the dermis) or no efficacy due toinadequate fluence at depth.

At the other end of the range, a larger spot size is desirable primarilybecause of enhanced coverage rate. For example, at a spot size between 2cm² and 4 cm² spot size per pulse, entire legs could be treated in lessthan 30 minutes, assuming a pulse repetition frequency of roughly onepulse per second. However, for a given output fluence and pulseduration, the optical peak power required scales linearly with the spotsize, and the cost and weight become prohibitive once the spot size getsabove approximately 1.0 to 2.0 cm².

Skin Color

A parameter that is not a characteristic of the output pulses of adermatologic treatment device, but that has a significant influence onthe effect of light-based treatment, is skin color. People with fairskin, e.g., of Scandinavian descent (so-called Type I), can handleperhaps six to eight times the fluence on the skin compared to a blackperson with so-called type VI skin. With good contact cooling, a severalhundred millisecond pulse, an 800 nm source and Type I skin, an outputfluence as high as 100 J/cm² would be usable without significantepidermal injury. However, most Caucasians have type II or type IIIskin, and 50 j/cm² might be the damage limit. For darker skin, the limitmay be closer to 30 J/cm². Although in a preferred embodiment, only afixed output fluence is generated by the device (as well as only asingle pulse duration being factory set), due to the various skin typesof users, an alternative embodiment of the apparatus includes means oflowering the output fluence either continuously or discretely in ahigh—medium—low embodiment, where the high setting still corresponds toa maximum potential fluence at the eye of a person below the maximumpermissible exposure (MPE) as detailed below. The advantage would bethat darker-skinned persons may find the high setting painful, andtherefore might prefer the medium or low setting, while stillmaintaining acceptable efficacy.

Eye Safety

Eye Safety Overview

Increased divergence and reduced spatial coherence, and resultingincrease in eye safety, is accomplished by incorporating into the pathof the beam of light within the apparatus, a diffusing material throughwhich the light travels prior to leaving the apparatus, as in the secondembodiment shown in FIG. 2A. Alternatively, the divergence may beincreased and spatial coherence reduced by incorporating into the devicea diffusing surface upon which the beam strikes prior to leaving thedevice, as in the third embodiment shown in FIG. 2B.

To compensate for any light that is absorbed within the apparatus by theintroduction of the diffuser, the output power from the light sourcewithin the apparatus can be increased. Alternatively, the diffusingmaterial or diffusing surface can be chosen to be substantiallynon-absorbing and the light source housing can be constructed so thatthe internal surfaces are substantially non-absorbing so thatsubstantially all of the light will be emitted from the output apertureof the apparatus, albeit after one or more scattering events from thediffusing material or diffusing surface, or light source housing.

Although the fluence of the light emitted by the output aperture willgenerally decrease as it propagates away from the apparatus due to thedivergent nature of the beam, many of the chromophores within the skinthat are targeted by light-based treatments are near the surface of theskin. If the target is much closer to the surface of the skin than thesize of the output aperture of the apparatus, there will be littledecrease of fluence at the chromophore due to divergence of theemission. Since skin itself is a highly scattering medium for much ofthe electromagnetic spectrum, the decrease in fluence at the target whenusing a very divergent source with little or no spatial coherence isrelatively insignificant when compared to the fluence at the targetproduced by a collimated light source that has equal fluence at thesurface of the skin; provided that the distance from the output windowor aperture of the source to the target beneath the skin surface issmall compared to the lateral dimension of the source (e.g., thediameter of the output window).

Calculations of Maximum Permissible Exposures and Fluences at the Eye ofa Person

To evaluate eye safety under the ANSI, IEC or ICNIRP guidelines, twovalues are calculated and compared. The first is the Maximum PermissibleExposure (MPE). This value is the fluence or irradiance that isconsidered safe for the human eye, measured at the cornea. The actualvalue of the MPE varies greatly depending on the characteristics of thelight source in question; specifically, the source wavelength, pulseduration, coherence, and, if incoherent (e.g., from a diffuse source)the angle formed by the dimension of the source and its distance fromthe cornea (the so-called angular subtense that determines the size ofthe corresponding image of the source on the retina; see InternationalStandard IEC 60825.1, “Safety of Laser products—Part 1: Equipmentclassification, requirements and user's guide”, Edition 1.2, August2001; p. 11.).

The second value “F_(cornea)” is the fluence produced at the cornea froma particular light source, as measured through a pair of apertureslimiting the angle of acceptance to 100 milliradians (see IEC 60825.1,above, p. 40, NOTE 2, sub-note d.). The value of F_(cornea) depends uponboth the fluence produced by the device at its output (the “outputfluence”), as well as how the light diverges from the output as itpropagates toward the eye. For any light source, if F_(cornea) is lessthan the MPE for all possible distances between the source and the eye,the device is considered eye-safe. Conversely, a light source thatproduces, at any particular distance, a value for F_(cornea) thatexceeds the MPE is considered hazardous.

For wavelengths of light between 400 nm and 1,050 um, and pulsedurations between 18 microseconds and 10 seconds, the MaximumPermissible Exposure (MPE) at the cornea is given by the followingequation:

MPE(J/cm²)=1.8*10⁻³ t ^(0.75) C ₄ C ₆  [Eq. 1]

where

t is the pulse duration in seconds;

C₄ is a correction factor for the wavelength λ of light, having thefollowing values:

for λ greater than 400 nm but less than 700 nm (visible light), C₄=1;

for λ greater than 700 nm but less than approximately 1100 nm(near-infrared light),

C ₄=10^(0.002(λ-700))  [Eq. 2]

note that C₄ increases from a value of 1 at 700 nm and has a value of 5at 1,050 nm;

C₆ is a correction factor that is equal to 1 for coherent sources (thisis strictly correct for sources that have a spatial coherence near thediffraction limit; for multimode sources or for arrays of coherentsources the calculation is more complex); and for diffuse, extendedsources is given by C₆α/α_(min) where α_(min) is equal to 1.5milliradians and α is the angular subtense of the source, i.e.

α=2 tan⁻¹(d/2r)≈d/r  [Eq. 3]

where d is the diameter of the source and r is the distance from thesource to the cornea.

Equation 3 applies only up to an angular subtense of 100 milliradians;above this angle, a value of 66.7 is used for C₆.

Two cases are considered below to exemplify the eye hazard associatedwith typical current devices for dermatologic treatment:

1. A visible, coherent source (e.g., a laser), having a circular outputaperture of one centimeter squared (diameter of 1.13 cm) and a 30millisecond pulse duration;

2. An incoherent, directed source (e.g., a flashlamp) having arectangular output aperture of 1 cm by 2 cm and a 30 ms pulse duration.

Example 1

Visible, coherent source (e.g., laser)

For a source of diameter d=1.13 cm, the angular subtense of the sourcevaries depending on the distance r from the eye; however, because inthis example the source is a laser in the visible region of the spectrum(in this example it is assumed that the laser is highly spatiallycoherent), both C₄ and C₆ are equal to 1, and the maximum permissibleexposure at the cornea given by Equation 1 is:

MPE=1.8*10⁻³ t ^(0.75) C ₄ C ₆=1.8*10⁻³(0.072)(1)(1)=1.3*10⁻⁴ J/cm²

or 130 microjoules per square centimeter. This fluence is of the orderof 100,000 times lower than the fluence involved in the therapeuticdermatologic treatment of typical skin problems such as hair-regrowthinhibition. It is of course true that the fluence exiting the 1 cm²laser aperture could be much higher than the 130 μJ/cm² figurecalculated above; for eye safety it is understood that only the fluenceat the cornea, F_(cornea), be no higher than this figure for the lasersource in this example. But such a source, if it is to be efficaciousfor the dermatologic treatments mentioned, would produce at least a fewjoules per square centimeter at its exit aperture, and it is illustratedbelow that this type of source will always exceed the MPE at somedistance. For example, suppose for eye safety reasons that the beam isdesigned to be highly divergent upon leaving the exit aperture; forexample, by passing the beam through a very fast f/0.8 concave lens asshown in FIG. 4. (An f/0.8 lens has a focal length equal to 0.8 timesits diameter.) This beam exits the lens at an angle φ of about 0.56radians, or 32 degrees. The fluence at a distance r from the exitaperture is given by (this is approximately correct for a Gaussian beamfrom a diffraction-limited laser):

Fluence F≈4Q/Π(rφ)²  [Eq. 4]

Where Q is the energy of the source. So for a source of 5 J/cm² outputfluence from a 1 cm² aperture, the fluence at a distance of, forexample, 20 cm (i.e. the output aperture of the device is 20 cm from theeye) is approximately 50 mJ/cm² still several thousand times above theMPE. Any adjustment factors for pulse duration or longer wavelength toincrease the MPE would not be nearly sufficient to make this device eyesafe; for example, increasing the wavelength to 1050 nm and the pulseduration to 300 ms results in only a roughly 30-fold increase in MPE, toabout 4000 μJ/cm² (i.e., increase due 1970 to pulse duration is(300/30)^(0.75) or about 5.6; increase in A from visible to 1050 nmincreases C₄ from 1 to 5; so combined increase is 5.6 times 5, or abouta factor of 28).

Example 2

An incoherent, directed source (e.g., a flashlamp)

A popular device for hair-regrowth inhibition as well as for facial“rejuvenation” utilizes a flashlamp with visible and near infraredoutput and an exit aperture of 1 cm by 2 cm, and an output energy of 80J (40 j/cm²) (see Node, L, “Are lasers more dangerous than IPLinstruments?” Lasers in Surgery and Medicine, Supplement 15, 2003, p. 6;and poster presentation at corresponding conference). Such sourcestypically have a directed output of about plus or minus 20 degrees, i.e.a solid angle Ω of about 0.4 steradians: If it is assumed 1985 that(very roughly) half of the output energy is in the visible, and half isin the 700 nm-900 nm range, a value of the wavelength correction factorC₄ of ˜1.3 is appropriate. The conclusions of this section areinsensitive to this parameter in any case. Because this device emitsincoherent light, the correction factor C₆ appropriate for “extendedsources” can be greater than one, and in fact will reach 66.7 when theangular subtense of the source is 100 milliradians, i.e. when the sourceis roughly 15 cm from the eye (see International Standard IEC 60825-1,p. 52. For non-circular sources the angular subtense is the arithmeticmean of the larger and smaller angular dimensions of the source). Itshould be noted that, once the source subtends an angle greater than 100milliradians (i.e. comes yet closer to the eye) the hazard to the eyeremains the same, because although the irradiance on the corneaincreases, the image area on the retina increases proportionally. FromEquation 1:

MPE(J/cm²)≈1.8*10⁻³ C ₄ C ₆=1.8*10⁻³(0.030)^(0.75)*1.3*66.7=11 mJ/cm²

The fluence F at a distance r from a source of energy Q directed into asolid angle .OMEGA. is approximately:

F≈Q/(r ²Ω)=80/(15²*0.4)=890 mJ/cm²

Thus, in this case

F _(cornea)=890 mJ/cm²

or approximately 80 times in excess of the MPE; still an extreme eyehazard. To make this device eye safe the fluence would have to bereduced by this factor, i.e., from 40 J/cm² to ˜0.5 J/cm², significantlybelow the fluence necessary to perform therapeutic photothermaldermatologic treatment.

A Proposed Device in Accordance with a Preferred Embodiment

Calculations analogous to those above can be done for an embodiment ofthe invention herein, as follows. As shown in FIG. 5, a light source310, which can be either a coherent source such as a laser or anincoherent source such as a flashlamp, impinges on a diffuser 320. Thediffuser in turn emits the scattered light preferably as anapproximately Lambertian source in the forward direction (see EarleBrown, Modern Optics, Reinhold Publishing Corporation, 1965; p. 225).Light backscattered from the diffuser toward the laser or flashlamp canbe reflected to impinge once again on the diffuser by incorporatingreflective walls in the chamber 330 and on the surface of light sourceholder 340 that faces chamber 330. It should be noted, however, thatsuch reflective walls only serve to improve the overall efficiency andspatial uniformity of the device and are in no way essential to theinvention. In addition, the diffuser 320 need not be located at the exitaperture, but may be recessed within chamber 330; in this case the wallsof chamber 330 between the diffuser 320 and the exit aperture should benon-absorbing. It should also be noted that the diffuser has the addedadvantage of removing any “hot spots” from the light source; i.e., asource such as an array of diode laser emitters has much higherintegrated radiance in some directions than in others; such localizedvariations will be smoothed out by a diffuser. In this embodiment a diskdiffuser of the Oriel type is described, but the invention can also beeffected with a different type of diffuser, as defined earlier.

For the sole purpose of providing a concrete example, let us assume thatthe device has a circular output aperture of area one square centimeter,as in Example 1 above. Let us further assume that the device has awavelength of 800 nm. From Equation 2, C₄ is equal to 1.58. As inExample 2 above, we also assume that the device is at a distance fromthe cornea such that the source (e.g., the diffuser located at theoutput aperture) subtends an angle of 100 milliradians (C₆=66.7). For asource of 1.13 cm diameter (1 cm² area) this distance is about 11.3 cm.Under these conditions, from Equation 1:

MPE(J/cm²)=1.8*10⁻³ t ^(0.75) C ₄ C ₆=1.8*10⁻³(0.072)(1.58)(66.7)=13.7mJ/cm²

For a Lambertian source, the fluence at a distance r (when lookingdirectly into the source) for a source of energy Q is given by

F(J/cm²)=Q/Πr ²  [Eq. 5] (see International Standard IEC 60825.1, p.79);

Thus, for our source at a distance of 11.3 cm, the fluence at the corneais equal to the MPE of 13.6 mJ/cm² when Q is equal to 5.5 joules. Sinceour source has an aperture of 1 cm², this corresponds to a sourcefluence of 5.5 J/cm². Thus our invention can have a source fluence of5.5 J/cm² for providing an intended photothermal injury to the skin andyet have an output below that which would result in an exposure to theeye in excess of the MPE:

F _(source)=5.5 J/cm²

F _(cornea)=MPE=13.7 mJ/cm²

As stated above, for this source to be considered eye safe, the fluenceat the cornea from the device must be less than the calculated MPE forall distances between the source and the eye, not merely the distancechosen in the above example. This can be shown to be true, as follows.

For distances less than 11.3 cm (i.e. as the output aperture of thesource is drawn closer to the eye, causing the angular subtense of thesource to exceed 100 mrad) the MPE remains the same. With decreasingdistance, the fluence from the source increases, but F_(cornea) remainsconstant because, as described above, it is measured through apertureslimiting the angle of acceptance to 100 mrad. Thus, if F_(cornea) isless than the MPE at a source distance corresponding to an angularsubtense of the source of 100 mrad, it is also safe at lesser distances.

Considering now the opposite case, where the source is moved fartherfrom the eye than 11.3 cm, two cases will be considered: that case wherethe distance from the source to the eye is such that its angularsubtense is more than 1.5 mrad but less than 100 mrad (for a source of1.13 cm diameter, distances between 11 cm and 750 cm) and that casewhere the source subtends an angle of less than 1.5 mrad (distances ofgreater than 750 cm). In the first case, the MPE decreases linearly withincreasing distance, but from Equation 5, F_(cornea) decreases as thesquare of the distance. Thus, if

F _(cornea)<MPE at α=100 mrad

then

F _(cornea)<MPE for 1.5 mrad<α<100 mrad

Considering now the last case, where the distance from the source to theeye is such that the angular subtense is less than 1.5 mrad (for thesource above, distances of greater than 750 cm), the values for MPE andF_(cornea) vary as follows: as the distance increases, the MPE remainsconstant, but as above, F_(cornea) continues to decrease as the squareof the distance. Thus one can conclude that the above source is safe atany distance.

As introduced above, one or both of the following additional features ispreferably included to allow even higher device fluences that arenonetheless still eye-safe. These features include an increase of thepulse duration of the light (e.g., from 30 ms to 300 ms), and anincrease in the wavelength of the light (e.g., from visible toinfrared); both of which result in a higher MPE for the eye and thusallow an increased therapeutic output that is still eye-safe. Thebenefits of each of these elements (diffuse source, extended pulseduration, and longer wavelength) can be quantified, as described aboveand below. In short summary, however, pulse durations in excess of 100ms and wavelengths above 700 nm are preferred, while as maxima, pulsedurations are maintained at or below 500 ms and wavelengths belowapproximately 1100 nm.

In order to further enhance the utility of the device and its use, thepulse duration can also be extended to preferably 300 ms from 30 ms, orin a preferred range between 100 ms and 500 ms. In a number oftherapeutic dermatologic procedures including light-based hair-regrowthinhibition, pulse durations of 300 ms or greater are and/or may be aneffective optimum. From Equation 1, in this case the MPE increases by afactor of (0.3/0.03)^(0.75) or about 5.6. Thus the light source in ourexample can have an output fluence 5.6 times greater than calculatedabove, or approximately 31 J/cm², and it will still not exceed the MPEat any distance.

Note that this calculated value of 31 J/cm² for a source fluence that iseye-safe agrees well with the corresponding value derived from theAccessible Emission Limit (AEL) as determined by the CDRH for a Class Ilaser device. Devices below the Class I AEL are considered to beeye-safe and therefore require no specific warning labels or othercontrols. From Table I of 21 CFR 1040.10, a laser device meets the ClassI AEL if its integrated radiance is less than the value below:

AEL=10k ₁ k ₂ t ^(1/3) J/(cm² sr).

Since, for our source,

k₁=1.56;

k₂=1; and

t^(1/3)=(0.300)^(1/3)=0.67,

then, AEL=10.4 J/(cm² sr).

For a Lambertian source, the source fluence (radiant exposure) isrelated to the integrated radiance L through the formula:

F _(source) =ΠL; thus

F _(source)(max)=(3.14 sr)(10.4 J/(cm² sr))=32.6 J/cm²

Thus, the device will be below the Class I Accessible Emission Limit ifthe source fluence is less than 32.6 J/cm², a value that agrees wellwith the 31 J/cm² calculated earlier from the IEC limits for MaximumPermissible Exposure. There may be further calculations or methods fordetermining an eye safe limit as may be required by the FDA or adifferent standards setting organization or in a different country orsetting. Although any of these eye safe limits are understood to be atleast approximately the values calculated as the AEL and the MPE limits,the value used may differ and devices constructed accordingly may differin their output limitations. Any such adhered to or acknowledgedreasonable eye safety limitation is intended to be included within themeaning and use of the term “eye safe” as used in the presentapplication.

Further Optical Design Considerations

The addition of a diffuser to a light-based dermatologic device topermit therapeutic fluences at the skin surface while ensuring eye-safeoperation is by no means limited to the preferred and alternativeembodiments described above and elsewhere herein. For example, a devicefor the treatment of acne using blue or other visible light can be madeeye safe at therapeutic fluences by the addition of a diffuser; and adevice for repigmentation of skin, or treatment of psoriasis orvitiligo, using ultraviolet light (290 nm to 400 nm) can also be mademuch safer with a diffuser added to the output aperture. In general,such devices contain incoherent sources with a directed output; i.e. theoutput beam expands from the output aperture by ˜±20 degrees,corresponding to a solid angle of about 0.4 steradians. By the additionof a diffuser, the output propagates into a full 2Πsteradians; if thediffuser creates a Lambertian distribution of the light (as is the casewith an Oriel-type diffuser) the angular dependence of the outputfluence will have the well-known cosine dependence, while other elementsalso described as diffusers for the purposes of this application mayhave a more general variation of fluence with viewing angle. Whentypical devices without a diffuser (i.e. devices which may have, forexample, a light output spreading into .about. 0.4 steradians) areviewed on-axis, i.e. directly into the source, the addition of thediffuser (backed by a chamber having reflective walls) reduces thefluence at the cornea by the ratio of (0.4/Π), or about 0.13, withoutaffecting the fluence of the device when applied to the skin. Thus adevice that produces a fluence at the cornea which exceeds the MPE by upto eight times can be made eye safe by the addition of a diffuser.

It should be noted that the fluence can be increased by up to anadditional factor of two (while still remaining eye-safe) by alteringthe output distribution of the light from Lambertian to that approachinga uniform source. This can be effected, for example, by creatingconcentric micro-grooves (either by diamond-machining of sapphire orcasting of plastic) such that an increased fraction of the light isrefracted into higher angles, as illustrated at FIG. 3B, orincorporating a point source and mirrored chamber design as illustratedat FIG. 3D.

The output pulses of the apparatus described above are described interms of energy (i.e., radiant exposure and integrated radiance) ratherthan in terms of power (i.e., irradiance and radiance); but theinvention applies equally to devices and/or methods characterized eitherby energy or power.

ALTERNATIVE EMBODIMENTS

Preferred and alternative embodiments of the invention may also includeany one or a combination of the following elements. First, as describedearlier, the heat removal element may be a thermal battery that is“recharged” (i.e., heat is removed) or replaced prior to use and absorbsheat during use. The thermal battery may be a phase-change material,such as ice, certain paraffin-like waxes or salts such as TEA29 fromTEAP Energy, or may be a high-heat capacity material like copper oraluminum or water, or may be a compressed gas or liquid that cools byexpansion to lower pressure. Second, a pigmentation sensor may beincluded that senses the amount of pigment in the skin. Such a sensormay be used to adjust output parameters such as pulse duration or pulseenergy or to prohibit operation for pigmentation levels higher than apre-selected threshold. Third, a means of operation that is sliding,rather than sequential spot-wise treatment, may be employed. By sliding,it is meant that the device is operated by continuously sliding theactive area of the device across the skin. The light may be delivered inpulses or continuously. The device may provide feedback to the user tohelp maintain dosimetry within a given range and/or may have a mechanismor internal feedback, such as provided by an optical or mechanicalsensor, to help maintain dosimetry within a given range. Fourth,non-contact cooling may be employed, such as spray cooling or liquidcooling or cooling with an gel applied to the skin. Fifth, reflective ordiffusive surfaces or elements on or within the device may be used thatmay redirect light that has been scattered back to the device from theskin back into the skin. Such redirection of remitted light may occur byspecular or diffuse reflection, such as from a partially transmissivediffuser near the output aperture or from reflective surfaces within oron the device. (As stated earlier, the term “reflective” is used in thiscontext to include remissive surfaces.)

In addition to hair-regrowth inhibition, the invention can also beadvantageously applied to other dermatology applications, includingtreatments for acne, benign pigmented lesions, vascularity, skintexture, skin wrinkles, and “photo-rejuventation” which is generallyaccepted in the field to mean skin treatment for pigmented lesions(including brown and red spots), vascularity (including the destructionof small blood vessels), and/or skin tone, skin texture, and skinwrinkles. For these applications, the invention may be modified from thepreferred embodiment hair-regrowth-inhibition device to make the devicemore optimal for the application. Some modifications to preferred andalternative embodiments described herein may be understood by thoseskilled in the art for alternative application in the above fields. Forexample, for the treatment of acne, a wavelength between 350-450 nm maybe chosen for its photodynamic effect on the porphrins produced by theacne bacteria. Alternatively, a wavelength in the range 1000-1800 nm maybe chosen to match the absorption spectrum of sebum, a major componentin acne. Likewise, for “photorejuvenation” a broad-band source, such asa flashlamp, may be used in order to simultaneously treat vascular andpigmented lesions and improve skin tone, texture, and wrinkles. Forphotorejuvenation, somewhat shorter wavelengths have been shown to beefficacious; e.g., 500-1100 nm. For dermatologic applications, theoutput fluences are generally desired to be greater than 4 J/cm² to beefficacious and the light is generally not eye-safe at these levels,although in accordance with a preferred embodiment, a diffuser isemployed to reduce the maximum fluence at a person's eye to below theMPE.

Also, “divergent” light sources such as diode laser light sources arereferred to herein. Light is defined herein as “divergent” when thedivergence angle .alpha. is greater than approximately ±6 degrees, wherethe divergence is defined as the geometric mean of the half-angle formedbetween the principal propagation axis (z-axis) and the full-widthhalf-maximum (FWHM) energy axes in the x and y coordinate directions.That is, if the divergence from the z-axis in the x-direction is ±α_(x)and the divergence in the y-direction is ±α_(y), then the divergence ±αequals the square root of the quantity ±α*±α_(y). For example, diodelaser bars typically have a FWHM beam divergence of about ±20 degrees inone axis and about ±5 degrees in the other axis, so have a typicaldivergence of about ±10 degrees as defined here. Thus, diode laser barsare a divergent light source. Diode lasers in general, flashlamps, andLED's are also typically divergent sources. A divergence value of 6degrees clearly differentiates “divergent” sources, such as diode lasersand flashlamps, from “collimated” sources, which in practice have somedivergence but typically less than 1 degree. Divergent light sources aresuperior to other light sources for achieving eye safety, in that asignificant portion of the light from such divergent sources strikingthe diffuser is already partially directed at significant angles fromthe principal propagation direction. Thus the task of the diffuser tospread the light into large angles is simplified.

While an exemplary drawing and specific embodiments of the presentinvention have been described and illustrated, it is to be understoodthat that the scope of the present invention is not to be limited to theparticular embodiments discussed. Thus, the embodiments shall beregarded as illustrative rather than restrictive, and it should beunderstood that variations may be made in those embodiments by workersskilled in the arts without departing from the scope of the presentinvention, as set forth in the appended claims and structural andfunctional equivalents thereof.

In addition, in methods that may be performed according to preferredembodiments herein and that may have been described above, theoperations have been described in selected typographical sequences.However, the sequences have been selected and so ordered fortypographical convenience and are not intended to imply any particularorder for performing the operations, unless expressly set forth in theclaims or as understood by those skilled in the art as being necessary.

1-78. (canceled)
 79. A dermatologic treatment apparatus, comprising: alight source providing pulses of light having an output fluence of 4-100J/cm² at a target area of a patient and having sufficient fluence tocause hair removal at the target area; an optical apparatus fordistributing light from the light source substantially uniformly acrossan input of a diffuser, wherein the diffuser diffuses the lightsufficiently to cause the apparatus to be eye-safe during treatmentwhile maintaining sufficient fluence to cause hair removal at the targetarea of the patient; a contact sensor configured to detect contact withthe skin; and control circuitry configured to enable the light source inresponse to the contact sensor detecting contact with the skin; whereinthe diffuser and the contact sensor act as independent eye safetyfeatures.
 80. The dermatologic treatment apparatus of claim 79, whereinthe diffuser has substantially the same area as the input.
 81. Thedermatologic treatment apparatus of claim 79, wherein the diffuser islarger in area than the input.
 82. The apparatus of claim 79, whereinthe light source is divergent.
 83. The apparatus of claim 79, whereinthe optical apparatus distributes light from the light source acrosssubstantially all of the diffuser.
 84. The apparatus of claim 79,wherein a principal optical axis of light emitted by the light sourcestriking the diffuser is not parallel to the normal of the surface ofthe diffuser.
 85. The apparatus of claim 85, wherein the light sourcecomprises one or more laser diode bars.
 86. The apparatus of claim 82,wherein the light source comprises one or more diode lasers.
 87. Adermatologic treatment apparatus, comprising: a light source providingcoherent light of 4-100 J/cm² at a target area of a human and havingsufficient fluence to effect a hair-removal dermatological treatment atthe target area; an optical apparatus, having an outlet, thatcommunicates the fluence substantially across the outlet; an opticaldiffuser that diffuses the light so that the light emitted from theapparatus is eye safe during the hair removal dermatological treatment;a contact sensor configured to detect contact with the skin; and controlcircuitry configured to enable the light source in response to thecontact sensor detecting contact with the skin; wherein the opticaldiffuser and the contact sensor act as independent eye safety features.88. The dermatologic treatment apparatus of claim 87, wherein thefluence is sufficient that the hair removal is permanent.
 89. Theapparatus of claim 87, wherein the optical diffuser comprises at leastone of a group including a transmissive diffuser and a reflectivediffuser.
 90. The apparatus of claim 87, wherein the optical diffuser isa transmissive diffuser and comprises a bulk scattering diffuser medium.91. The apparatus of claim 87, wherein the optical apparatus distributesthe light substantially uniformly across the outlet.
 92. The apparatusof claim 87, wherein the light is primarily within a spectral band of500 nm to 1100 nm.
 93. The apparatus of claim 87, wherein the lightsource includes one or more diode lasers.
 94. The apparatus of claim 87,wherein a principal optical axis of light emitted from the light sourcestriking the diffuser is not parallel to the normal of the surface ofthe diffuser.
 95. The apparatus of claim 94, wherein the light sourcecomprises one or more laser diode bars.
 96. The apparatus of claim 87,wherein the light source provides pulses of light.
 97. A method forperforming a hair-removal procedure on a human using a lens-less devicecomprising a divergent light source, an optical outlet, a diffuser, anda hollow cylindrical mixer, the method comprising: directing the opticaloutlet of the lens-less device at a target area of a human; activatingthe divergent light source to emit a divergent beam of light toward theoptical outlet; the hollow cylindrical mixer increasing a spatialuniformity of the divergent light from an input end of the mixer to anoutput end of the mixer; and the diffuser diffusing the light so thatthe light emitted from the optical outlet of the lens-less device is eyesafe; and wherein the light emitted from the optical outlet of thelens-less device has a fluence of 4-100 J/cm2 across the optical outletand sufficient fluence to effect a hair-removal dermatologicaltreatment.